Category Archives: taxonomy

The history of Systematics: Brisson’s system

by Piter Kehoma Boll

Previously, we saw that Linnaeus classified animals into 6 classes: Mammalia, Aves, Amphibia, Pisces, Insecta and Vermes and retained that system in future editions of Systema Naturae. At the same time that Linnaeus was publishing the 10th edition of Systema Naturae, which is the first work to use binomial nomenclature for animals, Brisson, a French zoologist, was creating his own system of classification.

Brisson decided to classify animals into 9 classes: Quadrupeda, Cetacea, Aves, Reptilia, Pisces cartilaginosi, Pisces proprie dicti, Insecta, Crustacea and Vermes. He describes the characters of animals in each class in his work “Regnum animale in classes IX. Distributum sive synopsis methodica”.

Class 1. Quadrupeda: hairy body, at least in some areas, and four feet.

Class 2. Cetacea: naked and elongate body, fleshy fins, horizontally flat tail.

Class 3. Aves: body covered by feathers, corneous bill, two wings, two feet.

Class 4. Reptilia: either naked body and four feet or scaly body and either four or no feet, and breathing through lungs.

Class 5. Pisces cartilaginei: cartilaginous fins and breathing through openings to naked gills.

Class 6. Pisces proprie dicti: fins consisted of little bones and breathing with gills covered by a movable and partially ossified cover.

Class 7. Crustacea: head equipped with antennae, and eight or more feet.

Class 8. Insecta: before last metamorphosis, with several stigmata or breathing organs; after last metamorphisis, head equipped with antennae, and six feet.

Class 9. Vermes: the body, or at least part of it, retractile, without antennae, feet or stigmata.

In this same work, he describes in detail the first two classes. The class Aves is described in a separate work, “Ornithologia, sive, synopsis methodica sistens avium divisionem in ordines, sectiones, genera, species, ipsarumque varietates”, but the remaining classes are never presented, so I will have to deal with those three only.

Class 1. Quadrupeda

This class is composed by all mammals known at the time, except for the cetaceans, which were in the following class, Cetacea. Brisson divided quadrupeds into 18 orders, but did not gave them names, only described them based on the number of teeth and types of nails. Linnaeus used dentition as the main character to classify mammals, but did it using different criteria.

Class 2. Cetacea

This class was composed by the cetaceans and was divided into 4 orders, each with a single genus. The orders were based on the (apparent) distribution of teeth.

In the following image you can see the classification of both Quadrupeda and Cetacea and their comparison to Linnaeus’ 1767 system.

Comparison of Linnaeus’ and Brisson’s systems for mammals. Asterisks indicate genera that are still valid today and were created by the respective authors. A † indicate a genus that is no longer valid.

Some curiosities when we compare mammals in both systems:

1. Linnaeus’ genus Trichechus included manatees and walruses. Brisson classified walruses into a separate genus, Odobenus, but included manatees in the genus Phoca, together with seals and sea lions!

2. Linnaeus included weasels and otters in the genus Mustela and civets in the genus Viverra. Brisson, on the other hand, put civets in the genus  Mustela, together with weasels, but put otters in a separate genus, Lutra.

3. While Linnaeus put hyaenas with dogs in the genus Canis and badgers with bears in the genus Ursus, Brisson had separate genera for hyaenas and badgers, named Hyaena and Meles.

4. Brisson put mice and rats in the genus Mus, dormice in the genus Glis and South-American short-tailed rodents, such as cavies and pacas, in the genus Cuniculus. Linnaeus had them all in Mus.

5. Brisson separated giraffes in their own genus, Giraffa, while Linnaeus classified them in the genus Cervus with deer.

Class 3. Aves

Brisson’s classification of birds was very different from that of Linnaeus. There were many more orders and genera. In fact, some genera used by Linnaeus in 1767 were created by Brisson. See below how complex the relationship of one system to the other is:

Comparison of Linnaeus’ and Brisson’s classification of birds. See the huge difference between both systems. Asterisks indicate genera that are still valid today and were created by the respective authors. A † indicate a genus that is no longer valid.

Unfortunately, Brisson never published his classification of other animals, so we must move on to the next authors in the following posts.

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Brisson M-J (1762). Regnum animale in classes IX. Distributum, sive, Synopsis methodica. Lugduni Batavorum apud Theodorum, Haak. 316 pp.

Brisson M-J (1763a). Ornithologia, sive, synopsis methodica sistens avium divisionem in ordines, sectiones, genera, species, ipsarumque varietates. Apud Theodorum Haak, Lugduni Batavorum : 534 pp.

Brisson M-J (1763b). Ornithologia, sive, Synopsis methodica sistens avium divisionem in ordines, sectiones, genera, species, ipsarumque varietates. Apud Theodorum Haak, Lugduni Batavorum : 542 pp.


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The history of Systematics: Systema Naturae from 1758 to 1767-1770

by Piter Kehoma Boll

In a series of previous posts, I detailed the classification of living beings by Linnaeus in his work Systema Naturae as presented in its 10th edition, published in 1758. Here, I will present it in a summarized way and show changes that happened from the 10th edition to the 13th edition published in two parts, one 9 years later in 1767, dealing with animals, and one 12 years later, in 1770, dealing with plants.


Linnaeus classified animals in 6 classes: Mammalia, Aves, Amphibia, Pisces, Insecta and Vermes.

1. Mammalia included mammals and in 1758 they were classified in 8 orders: Primates, Bruta, Ferae, Bestiae, Glires, Pecora, Belluae, Cete (see details here).

Linnaeus’ classification of Mammals in 1758 and 1767

In 1767 the order Bestiae no longer exists. Armadillos (Dasypus) were transfered to Bruta, pigs (Sus) to Belluae and the remaining genera to Ferae. Additionally, rhinoceroses (Rhinoceros) were transfered from Glires to Belluae and one bat species was transferred from the genus Vespertilio in Primates to a new genus, Noctilio, in Glires.

2. Aves included birds and in 1758 they were classified in 6 orders: Accipitrae, Picae, Anseres, Grallae, Gallinae, Passeres (see details here).

Linnaeus’ classification of birds in 1758 and 1767

In 1767, five new genera are seen in Picae: Buphaga, the oxpeckers, Trogon, the trogons, and Oriolus, the orioles (previously in the genus Coracias), Bucco, the puffbirds and Todus, the todies. One new genus appears in Anseres, Plotus, the darters. The order Grallae receives the new genera Palamedea, the seriemas and screamers, Parra, the jacanas, and Cancroma, the boat-billed heron. The order Gallinae is increased with the new genera Didus, the dodo (which was previously a member of the genus Struthio in the order Grallae), and Numida, the guineafowl (previously in the genus Phasianus). And, finally, the order Passeres received the new genera Pipra for the manakins (previously in Parus), Ampelis, the waxwings and cotings (previously in the genus Lanius in the order Accipitrae), Tanagra, the tanagers (previously in Fringilla) and Muscicapa, the flycatchers (previously in the genera Corvus and Motacilla).

It is also interesting to notice a change in the name of the order Accipitrae to Accipitres, and the genus Jynx is here written Yunx.

3. Amphibia included reptiles, amphibians and some fish and had 3 orders: Reptiles, Serpentes and Nantes (see details here).

Linnaeus’ classification of Amphibians in 1758 and 1767

The orders Reptiles and Serpentes remained the same. The order Nantes, which in 1758 included mainly cartilaginous fishes, in 1767 included a lot of genera that were previously classified in the class Pisces, especially in the order Branchiostegi (see below).

4. Pisces included most fish and had 5 orders: Apodes, Jugulares, Thoracici, Abdominales and Branchiostegi (see details here).

Linnaeus’ classification of fishes in 1758 and 1767

The genus Ophidion was transfered from the order Jugulares to Apodes and appears spelled Ophidium. The order Thoracici received the additional genus Cepola (red bandfishes) and the order Abdominales was increased with the genera Amia (the bowfin), Teuthis and Elops (the ladyfish), as well as the genus Mormyrus, previosly in the order Branchiostegi, which ceased to exist.

5. Insecta included arthropods and had 7 orders: Coleoptera, Hemiptera, Lepidoptera, Neuroptera, Hymenoptera, Diptera, Aptera (see details here).

Linnaeus’ classification of Insects in 1758 and 1767

The order Coleoptera received the new genera Lucanus (stag beetles, previously in Scarabaeus), Byrrhus (pill beetles), Gyrinus (whirligig beetles), Bruchus (pea weevils), Ptinus (spider beetles), HispaLampyris (glowworms). The genera Blatta and Gryllus were transfered to Hemiptera and mantises were removed from Gryllus and received their own genus, Mantis. Additionally, the lantern flies were removed from the genus Cicada and transferred to Fulgora. In the order Neuroptera, antlions were removed from the genus Hemerobius and transferred to a new genus Myrmeleon. In the order Hymenoptera, the cuckoo wasps were transferred from the genus Sphex to a new genus Chrysis.

6. Vermes included several worms, molluscs, echinoderms, cnidarians and hagfishes. There were 5 orders: Intestina, Mollusca, Testacea, Lithophyta and Zoophyta (see details here).

Linnaeus’ classification of worms in 1758 and 1767

From 1758 to 1767, the genus Furia, of a fictional species, was transferred from Intestina to Zoophyta, and the genus Teredo (shipworms) was transferred from Intestina to Testacea. A new genus, Sipunculus, was added to Intestina to include the peanut worms. In the order Mollusca, we find now the new genera Ascidia (sea squirts), Aplysia (sea hares), Terebella (some polychaetes, previously in Nereis) and Clio (some sea slugs). The genus Priapus, containing sea anemones, is now called Actinia. The order Testacea received the new genera Mactra (trough shells, previously in Cardium) and Sabella (fanworm, previously in Serpula). The order Lithophyta received the new genus Cellepora (for bryozoans). In the order Zoophyta we find the new genera Flustra (for bryozoans previously in Eschara), Vorticella (for ciliates previously in Hydra) and Chaos (for amoebas, previously in Volvox). An additional genus is seen in Zoophyta: Spongia (sponges), transferred from Algae, back in the plant kingdom


Plants had a much more complicated system than animals. There were the plants with regular flowers classified in classes and orders according to the number of male and female sexual organs, respectively (as you can read in detail in parts 1, 2, 3 and 4 of plants in Systema Naturae). Little has changed that except for some genera, as you can see in the table below.

Linnaeus classification of plants with regular hermaphrodite flowers in 1758 and 1770. See the image in higher resolution here.

The same is true for species in the classes Didynamia and Tetradynamia, which have flowers with stamens of different sizes. Little has changed in their classification.

Linnaeus’ classification of plants with flowers having stamens of two different sizes in 1758 and 1770.

Regarding the three classes characterized by flowers with clustered stamens, we can see two new orders in the class Monadelphia.

Linnaeus’ classification of plants having flowers with clustered stamens in 1758 and 1770.

In the class Syngenesia we can notice that the order Polygamia Superflua ceases to exist, with most of its species being transferred to Polygamia Aequalis, and a new order, Polygamia Segregata, is now present. In the class Gynandria a new order, Dodecandria, is created. See those two classes in more detail here.

Linnaeus’ classification of plants with stamens fused to each other or to the carpels in 1758 and 1770.

In the three classes of plants with male and female organs occurring in separate flowers, I think the most interesting novelty is that the genus Chara, which in 1758 was classified as a genus of algae, is now among the flowering plants in the class Monoecia, order Monandria.

Linnaeus’ classification of plants having male and female organs in different flowers in 1758 and 1770.

Finally, among the Cryptogams, the “plants without flowers”, little has changed except for the transfer of Chara to the flowering plants and Spongia to the animal kingdom.

Linnaeus classification of Cryptogams in 1758 and 1770

While Linnaeus continued to develop his own system, other classifications were being proposed. We’ll start to take a look at them in the next chapters.

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Linnaeus, C. (1758) Systema Naturae per regna tria Naturae…

Linnaeus, C; (1967) Systema Naturae per regna tria Naturae….

Linnaeus, C. (1770) Systema Naturae per regna tria Naturae…


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The history of Systematics: Plants in Systema Naturae, 1758 (Part 9)

by Piter Kehoma Boll 

The last part of the series is finally here! See also parts 1, 2, 3, 4, 5, 6, 7 and 8. The only class that remains to be introduced is Cryptogamia, the plants without flowers.

24. Cryptogamia (“hidden marriages”)

“Marriage is celebrated privately”, i.e., sexual organs are not clearly visible.

24.1 Filices (ferns)Equisetum (horsetails), Onoclea (sensitive fern), Ophioglossum (adder’s-tongue ferns), Osmunda (royal ferns), Acrostichum (leather ferns), Polypodium (polypodies), Hemionitis (hemionitises), Asplenium (spleenworts), Blechnum (hard ferns), Lonchitis (lonchitises), Pteris (brakes), Adiantum (walking ferns), Trichomanes (britstle ferns and lace ferns), Marsilea (water clovers), Pilularia (pillworts), Isoetes (quillworts).


Linnaeus’ order Filices included (from left to right, top to bottom) the common horsetail (Equisetum arvense), the sensitive fern (Onoclea sensibilis), the common adder’s tongue (Ophioglossum vulgatum), common royal fern (Osmunda regalis), golden leather-fern (Acrostichum aureum), Chinese brake (Pteris vittata), western hard fern (Blechnum occidentale), black spleenwort (Asplenium adiantum-nigrum), common polypody (Polypodium vulgare), Venus-hair fern (Adiantum capillus-veneris), lace fern (Trichomanes chinensis, now Sphenomeris chinensis), European water clover (Marsilea quadrifolia), common pillwort (Pilularia globulifera), and lake quillwort (Isoetes lacustris). Credits to Rob Hille (horsetail), Kurt Stueber (royal fern), Krzysztof Ziarnek (hard fern), Forest & Kim Starr (spleenwort, lace fern), H. Zell (polypody), Tato Grasso (Venus-hair fern), Daria Inozemtseva (quillwort), Wikimedia users JMK (brake), Keisotyo (water clover) and Kembangraps (pillwort), flickr user peganum (sensitive fern).

24.2 Musci (mosses): Lycopodium (club mosses), Porella (scaleworts), Sphagnum (sphagnums), Phascum (phascum mosses), Fontinalis (fountain mosses), Buxbaumia (bug mosses), Splachnum (dung mosses), Polytrichum (haircap mosses), Mnium (calcareous mosses), Bryum (common mosses), Hypnum (flat mosses).


Among the species in the order Musci there were (from left to right, top to bottom) the common club moss (Lycopodium clavatum), pinnate scalewort (Porella pinnata), prairie sphagnum (Sphagnum palustre), common fountain moss (Fontinalis antipyretica), common bug moss (Buxbaumia aphylla), Alpine haircap (Polytrichum alpinum), horn calcareous moss (Mnium hornum), silver moss (Bryum argenteum), cypress moss (Hypnum cupressiforme). Credits to Christian Fischer (club moss), Rafael Medina (scalewort), Bern Haynold (sphagnum), Hermann Schachner (haircap, silver moss), Bernard Dupont (calcareous moss), and Wikimedia users AnRo0002 (fountain moss) and Aconcagua (cypress moss).

24.3 Algae (algae): Jungermannia (leafy liverworts), Targionia (targionias), Marchantia (thallose liverwort), Blasia (blasia), Riccia (crystalworts), Anthoceros (hornworts), Lichen (lichens), Chara (stoneworts), Tremella (several jelly-like organisms), Fucus (brown and red algae), Ulva (sea lettuces and lavers), Conferva (several filamentous algae), Byssus (several crusty and wooly organisms), Spongia (sponges).


The diverse order Algae included (from left to right, top to bottom) the forest leafy liverwort (Jungermannia nemorea, now Scapania nemorea), common targionia (Targionia hypophylla), green tongue liverwort (Marchantia polymorpha), blasia (Blasia pusilla), floating crystalwort (Riccia fluitans), smooth horwort (Anthoceros laevis, now Phaeoceros laevis), map lichen (Lichen geographicus, now Rhizocarpon geographicum), common stonewort (Chara vulgaris), witch’s jelly (Tremella nostoc, now Nostoc commune), serrated wrack (Fucus serratus), common sea lettuce (Ulva lactuca), rock weed (Conferva rupestris, now Cladophora rupestris), golden wool (Byssus aurea, now Trentepohlia aurea), bath sponge (Spongia officinalis). Credits to Bernd Haynold (leafy liverwort, blasia), Luis Fernández García (targionia), Denis Barthel (green tongue), Christian Fischer (crystalwort), Fritz Geller-Grimm (lichen), Lairich Rig (witch’s jelly), Kristian Peters (sea lettuce), Bioimages (rock wed), JK Johnson (golden wool), Guido Picchetti (sponge) and Wikimedia users Oliver s. (hornwort), Mnolf (stonewort) and Citron (wrack).

24.4 Fungi (fungi): Agaricus (gilled mushrooms), Boletus (pore-bearing mushrooms), Hydnum (toothed mushrooms), Phallus (phallic mushrooms), Clathrus (finger-shaped fungi), Elvela (saddle-like mushrooms), Peziza (cup-shaped mushrooms), Clavaria (club-shaped mushrooms), Lycoperdon (ball-shaped mushrooms), Mucor (molds).


The order Fungi contained (from left to right, top to bottom) the field mushroom (Agaricus campestris), common red shelf-mushroom (Boletus sanguineus, now Pycnoporus sanguineus), sweet tooth (Hydnum repandum), common stinkhorn (Phallus impudicus), carnival candy slime-mold (Clathrus denudatus, now Arcyria denudata), vinegar cup (Peziza acetabulum, now Helvella acetabulum), sweet club-mushroom (Clavaria pistillaris, now Clavariadelphus pistillaris), grassland puffball (Lycoperdon cervinum, now Lycoperdon lividum), common pin-mold (Mucor mucedo). Credits to Nathan Wilson (field mushroom), Instituto Últimos Refúgios (shelf mushroom), H. Krisp (sweet tooth, vinegar cup), Jörg Hempel (stinkhorn), Bea Leiderman (slime mold), Francisco J. Díez Martín (club mushroom), Michel Beeckman (puffball) and James Lindsey (pin mold).

Here we can see that Linnaeus’ mess reached its limit. There are even animals classified as plants, as you can see sponges appearing as algae. Actually, the order Algae included species belonging to almost every currently recognized kingdom, from bacteria to animals, fungi, plants and heterokonts. The other orders are considerably more uniform.

We finished Linnaeus’ System! Yay!

I will make an additional post with a summary and then we can move on to changes that happened in following systems. See you there!

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Linnaeus, C. (1758) Systema Naturae per regna tria Naturae…

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The history of Systematics: Plants in Systema Naturae, 1758 (Part 8)

by Piter Kehoma Boll

This is the last part of Linnaeus’ classification of plants dealing with flowering plants (see parts 1, 2, 3, 4, 5, 6 and 7) and presents three classes composed by plants that contain more than one type of flower. The last part of the system (part 9) will deal with non-flowering plants.

21. Monoecia (“single house”)

“Husbands inhabit with women in the same house, but in different bedroom”, i.e., male and female organs occur in the same plant, but in different flowers.

21.1 Monoecia Monandria (“single house, single male”), male flowers having a single stamen: Zannichellia (horned pondweeds), Ceratocarpus (hornfruits), Hippomane (manchineels), Cynomorium (desert thumb).

21.2 Monoecia Diandria (“single house, two males”), male flowers having two stamens: Lemna (duckweeds).


The horned pondweed (Zannichellia palustris, left), the manchineel tree (Hippomane mancinella, center-left) and the desert thumb (Cynomorium coccineum, center-right) were classified in the order Monoecia Monandria, while the common duckweed (Lemna minor, right) was classified in the order Monoecia Diandria. Credits to Yu Ito (horned pondweed), Hans Hillewaert (manchineel, desert thumb) and Wikimedia user 3268zauber (duckweed).

21.3 Monoecia Triandria (“single house, three males”), male flowers having three stamens: Typha (cattails or bulrushes), Sparganium (bur-reeds), Zea (maize), Tripsacum (gamagrasses), Coix (Job’s tear), Olyra (carrycillo), Carex (true sedges), Axyris (pigweeds), Omphalea (cobnuts), Tragia (noseburns), Hernandia (hernandias), Phyllanthus (chamber bitters, Indian gooseberries and alike).


The order Monoecia Triandria included (from left to right, top to bottom) the common cattail (Typha latifolia), branched bur-reed (Sparganium erectum), maize (Zea mays), eastern gamagrass (Tripsacum dactyloides), Job’s tear (Coix lacryma-jobi), carrycillo (Olyra latifolia), carnation-sedge (Carex panicea), Jamaican cobnut (Omphalea triandra), Indian noseburn (Tragia involucrata) and chamber bitter (Phyllanthus urinaria). Credits to H. Zell (maize), Mason Brock (gamagrass), Alex Popovkin (carrycillo), Kristian Peters (sedge), and Wikimedia users AnRo0002 (cattail), Hugo.arg (bur-reed), Vinayaraj (Job’s tear, Indian noseburn), Carstor (cobnut) and Atsuko-y (chamber bitter).

21.4 Monoecia Tetrandria (“single house, four males”), male flowers with four stamens: Betula (birches and alders), Buxus (box), Urtica (nettles), Morus (mulberry trees).


The dwarf birch (Betula nana, left), the common box (Buxus sempervirens, center-left), the common nettle (Urtica dioica, center-right) and the black mulberry tree (Morus nigra, right) were classified in the order Monoecia Tetrandria. Credits to Uwe H. Friese (nettle), Fritz Geller-Grimm (mulberry tree) and Wikimedia users El Grafo (birch) and Abrimaal (box).

21.5 Monoecia Pentandria (“single house, five males”), male flowers with five stamens: Xanthium (cockleburs), Ambrosia (ragweeds), Parthenium (feverfews), Iva (marsh elders), Amarantus (pigweeds).


The common cocklebur (Xanthium strumarium, left), the common ragweed (Ambrosia artemisiifolia, center-left), the American feverfew (Parthenium integrifolium, center), the annual marsh elder (Iva annua, center-right) and the spiny pigweed (Amaranthus spinosus, right) were part of the order Monoecia Pentandria. Credits to Javier Martin (cocklebur), Meneerke Bloem (ragweed), Krzysztof Ziarnek (feverfew), and Forest & Kim Starr (pigweed).

21.6 Monoecia Hexandria (“single house, six males”), male flowers with six stamens: Zizania (wild rice), Pharus (stalkgrass), Solandra (a species of doubtful identifcation).

21.7 Monoecia Heptandria (“single house, seven males”), male flowers with seven stamens: Guettarda (beach gardenia).


The wild rice (Zizania aquatica, left) and the broadleaf stalkgrass (Pharus latifolius, center) were placed in the order Monoecia Hexandria, while the beach gardenia (Guettarda speciosa) was in the order Monoecia Heptandria. Credits to Michael Wolf (wild rice), Alex Popovkin (stalkgrass) and Cas Liber (beach gardenia).

21.8 Monoecia Polyandria (“single house, many males”), male flowers with many stamens: Ceratophyllum (hornworts), Myriophyllum (watermilfoils), Sagittaria (arrowheads), Theligonum (dog’s cabbage), Poterium (burnets), Quercus (oaks), Juglans (walnut trees), Fagus (beeches and chestnut trees), Carpinus (hornbeams), Corylus (hazels), Platanus (planes), Liquidambar (sweetgums).


Linnaeus included in the order Monoecia Polyandria (from left to right, top to bottom) the common hornwort (Ceratophyllum demersum), whorl-leaf watermilfoil (Myrophyllum verticillatum), common arrowhead (Sagittaria sagittifolia), common oak (Quercus robur), common walnut tree (Juglans regia), common beech (Fagus sylvatica), common hornbeam (Carpinus betulus), common hazel (Corylus avellana), Eastern plane (Platanus orientalis) and American sweetgum (Liquidambar styraciflua). Credits to Christian Fischer (hornwort, arrowhead), Piotr Panek (watermilfoil), Krzysztof Ziarnek (oak), H. Zell (walnut tree), Franz Xaver (hornbeam), André Karwath (hazel), Dimitar Nàydenov (plane), Kurt Stueber (sweetgum) and Wikimedia user Der Michels (beech).

21.9 Monoecia Monadelpha (“single house, single brothers”), male flowers with stamens fused in a single body by their filaments: Pinus (pines, larches, spruces and firs), Thuja (thujas), Cupressus (cypresses), Acalypha (acalyphas), Croton (crotons), Jatropha (physicnuts), Ricinus (castor oil plants), Sterculia (bastard poon tree), Plukenetia (Inca nut tree), Hura (possumwood).


The order Monoecia Monadelpha included (from left to right, top the bottom) the Swiss pine (Pinus cembra), eastern thuja (Thuja occidentalis), Mediterranean cypress (Cupressus sempervirens), Indian acalypha (Acalypha indica), garden croton (Croton variegatus, now Codiaeum variegatum), black physicnut (Jatropha gossypifolia), castor oil plant (Ricinus communis), bastard poon tree (Sterculia foetida), Inca nut (Plukenetia volubilis) and possumwood (Hura crepitans). Credits to Wouter Hagens (thuja), J. M. Garg (acalypha, croton, physicnut), Martina Nolte (castor oil plant), Raju Kasambe (bastard poon tree), Hans Hillewart (possumwood) and Wikimedia users Moroder (pine), Philmarin (cypress) and NusHub (Inca nut).

21.10 Monoecia Syngenesia (“single house, same generation”), male flowers with stamens united forming a cylinder: Trichosanthes (snake gourd), Momordica (bitter melons and luffas), Cucurbita (pumpkins, squashes, calabashes, watermelon), Cucumis (melons, cucumbers), Bryonia (bryonies), Sicyos (bur cucumber).

21.11 Monoecia Gynandria (“single house, female husband”), male flowers with stamens united to the (sterile) pistil: Andrachne (andrachne).


The order Monoecia Syngenesia included (from left to right) the snake gourd (Trichosanthes cucumerina), bitter melon (Momordica charantia), pumpkin (Cucurbita pepo), cucumber (Cucumis sativus), white bryony (Bryonia alba) and oneseed bur cucumber (Sicyos angulatus), while the order Monoecia Gynandria included the common andrachne (Andrachne telephioides, right). Credits to Florian Wickern (pumpkin), H. Zell (cucumber), Robert H. Mohlenbrock (bur cucumber), Vojtĕch Zavadil (andrachne), flickr user tanakawho (snake gourd) and Wikimedia users Prenn (bitter melon) and Sannse (bryony).

22. Dioecia (“two houses”)

“Husbands and women live in different bedrooms and houses”, i.e., male and female organs occur in different flowers and in different plants.

22.1 Dioecia Monandria (“two houses, single male”), male flowers having a single stamen: Najas (naiads).

22.2 Dioecia Diandria (“two houses, two males”), male flowers having two stamens: Vallisneria (eelgrasses), Cecropia (trumpet tree), Salix (willows).


The order Dioecia Monandria included a single species, the spiny naiad (Najas marina, left). The order Dioecia Diandria included the common eelgrass (Vallisneria spiralis, center-left), trumpet tree (Cecropia pelatata, center-right) and weeping willow (Salix babylonica, right). Credits to Stefan Lefnaer (naiad), Ori Fragman-Sapir (eelgrass), and Wikimedia users Cmales (trumpet tree) and Viaouest (willow).

22.3 Dioecia Triandria (“two houses, three males”), male flowers having three stamens: Empetrum (crowberries), Osyris (osyris), Excoecaria (blind-your-eye mangrove).


The black crowberry (Empetrum nigrum, left), osyris (Osyris alba, center) and blind-your-eye mangrove (Excoecaria agallocha, right) were part of the order Dioecia Triandria. Credits to Krzysztof Ziarnek (crowberry), Hans Hillewaert (osyris) and Wikimedia user Vengolis (blind-your-eye mangrove).

22.4 Dioecia Tetrandria (“two houses, four males”), male flowers having four stamens: Trophis (trophis), Batis (beachwort), Viscum (mistletoes), Hippophae (sea buckthorns), Myrica (bog myrtles and wax myrtles).


The beachwort (Batis maritima, left), common mistletoe (Viscum album, center-left), common sea buckthorn (Hippophae rhamnoides, center-right) and bog myrtle (Myrica gale, right) made up the order Dioecia Tetrandria. Credits to Forest & Kim Starr (beachwort), Karunakar Rayker (sea buckthorn), Sten Porse (bog myrtle) and Wikimedia user AnRo0002 (mistletoe).

22.5 Dioecia Pentandria (“two houses, five males”), male flowers having five stamens: Pistacia (pistachios and lentiscs), Zanthoxylum (prickly ashes), Ceratonia (carob tree), Iresine (Juba’s bush), Antidesma (heen embilla), Spinacia (spinach), Acnida (water hemp), Cannabis (hemp), Humulus (hop), Zanonia (zanonia), Fevillea (javillo).


The order Dioecia Pentandria included (from left to right, top to bottom) the pistachio (Pistacia vera), souther prickly ash (Zanthoxylum clava-herculis), carob tree (Ceratonia siliqua), Juba’s bush (Iresine celosia, now Iresine diffusa), spinach (Spinacia oleracea), hemp (Cannabis sativa), the common hop (Humulus lupulus), zanonia (Zanonia indica) and javillo (Fevillea cordifolia). Credits to Franz Xaver (Juba’s bush), Dinesh Valke (hemp), Fritz Geller-Grimm (hop), P. Acevedo (javillo) and Wikimedia users NAEINSUN (pistachio), Rickjpelleg (carob tree), Rasban (spinach) and Vinayaraj (zanonia).

22.6 Dioecia Hexandria (“two houses, six males”), male flowers having six stamens: Tamus (lady’s seal), Smilax (smilaxes), Rajania (rajanias), Dioscorea (true yams).


Linnaeus included the lady’s seal (Tamus communis, now Dioscorea communis, left), common smilax (Smilax aspera, center) and air yam (Dioscorea bulbifera, right) in the order Dioecia Hexandria. Credits to Alan Fryer (lady’s seal), Carsten Niehaus (smilax) and Dinesh Valke (yam).

22.7 Dioecia Octandria (“two houses, eight males”), male flowers having eight stamens: Populus (aspens and poplars), Rhodiola (golden root).

22.8 Dioecia Enneandria (“two houses, nine males”), male flowers having nine stamens: Mercurialis (mercuries), Hydrocharis (frogbits).


The order Dioecia Octandria included the common aspen (Populus tremula, left) and the golden root (Rhodiola rosea, center-left), while the order Dioecia Enneandria included the dog’s mercury (Mercurialis perennis, center-right) and the common frogbit (Hydrocharis morsus-ranae, right). Credits to Wikimedia users AnRo0002 (aspen), Amazonia Exotics U.K (golden root), BerndH (mercury) and Salicyna (frogbit).

22.9 Dioecia Decandria (“two houses, ten males”), male flowers with ten stamens: Carica (papaya tree), Kiggelaria (wild peach), Coriaria (coriarias), Datisca (datiscas).

22.10 Dioecia Polyandria (“two houses, many males”), male flowers with many stamens: Cliffortia (Cliffortias).


The order Dioecia Decandria included (from left to right) the papaya tree (Carica papaya), wild peach (Kiggelaria africana), huique (Coriaria ruscifolia) ad Asian datisca (Datisca cannabina), while the prickly cliffortia (Cliffortia ruscifolia, right) was one of the few members of the order Dioecia Polyandria. Credits to Vijayan Rajapuram (papaya tree), Franz Xaver (huique), H. Zell (datisca), and Wikimedia users JMK (wild peach) and Dwergenpaartje (cliffortia).

22.11 Dioecia Monadelphia (“two houses, single brothers”), male flowers with stamens fused in a single body by their filaments: Juniperus (junipers), Taxus (yews), Ephedra (joint pines), Cissampelos (velvetleaf), Adelia (adelias).


Among the members of the order Dioecia Monadelphia there were (from left to right) the Phoenician juniper (Juniperus phoenicea), European yew (Taxus baccata), common joint pine (Ephedra distachya) and velvetleaf (Cissampelos pareira). Credits to Isidre Blanc (juniper), Didier Descouens (yew), Dinesh Valke (velvetleaf) and Wikimedia user Le.Loup.Gris (joint pine).

22.12 Dioecia Syngenesia (“two houses, same generation”), male flowers with stamens fused into a cylinder: Ruscus (butcher’s brooms and poet’s laurel).

22.13 Dioecia Gynandria (“two houses, female husband”), male flowers with stamens united to the (sterile) pistil: Clutia (lightning bushes).


The common butcher’s broom (Ruscus aculeatus, left) was in the order Dioecia Syngenesia, and the common lightning bush (Clutia pulchella, right) was in the order Dioecia Gynandria. Credits to Fritz Geller-Grimm (butcher’s broom) and Wikimedia user JMK (lightning bush).

23. Polygamia (“many marriages”)

“Husbands with wives as well as unmarried ones live together in different bedrooms”, i.e., there are hermaphroditic flowers, as well as male-only or female-only flowers in the same species.

23.1 Polygamia Monoecia (“many marriages, single house”), hermaphrodite flowers occur in the same plant in which male-only or female-only flowers occur: Musa (banana trees), Ophioxylon (devil pepper), Celtis (hackberries), Veratrum (false hellebores), Andropogon (beard grasses, bluestems, spear grasses, lemon grasses, among others), Holcus (soft grasses, fountaingrasses, sorghums, among others), Apluda (Mauritian grass), Ischaemum (murainagrass), Cenchrus (sandspurs), Aegilops (goatgrasses), Valantia (valantias), Parietaria (pellitories), Atriplex (oraches), Dalechampia (dalechampias), Clusia (copeys), Acer (maples), Begonia (begonias), Mimosa (mimosas, shimbilloes, sennas, blackbeads, among others).


The diverse order Polygamia Monoecia included (from left to right, top to bottom) the banana tree (Musa paradisiaca, currently Musa × paradisiaca, a hybrid), devil pepper (Ophioxylon serpentinum, now Rauvolfia serpentina), Mediterraean hackberry (Celtis australis), white hellebore (Veratrum album, broomsedge bluestem (Andropogon virginicus), creeping soft grass (Holcus mollis), Mauritian grass (Apluda mutica), common murainagrass (Ischaemum aristatum), common sandspur (Cenchrus echinatus), bearded goatgrass (Aegilops triuncialis), wall valantia (Valantia muralis), upright pellitory (Parietaria officinalis), garden orache (Atriplex hortensis), common dalechampia (Dalechampia scandens), lesser copey (Clusia minor), red maple (Acer rubrum), Antillean begonia (Begonia obliqua), and touch-me-not (Mimosa pudica). Credits to Franz Xaver (banana tree), H. Zell (devil pepper), Krish Dulal (hackberry), Hedwig Storch (white hellebore), Harry Rose (bluestem), Krzysztof Ziarnek (soft grass), J. M. Garg Mauritian grass), Javier Martin (goatgrass), Radio Tonreg (pellitory), Stefan Lefnaer (orache), David J. Stang (copey), Yercaud Elango (begonia), flickr user Macleay Grass Man (sandspur) and Wikimedia users Keisotyo (murainagrass), Aroche (valantia), Aniprina (dalechampia), Famartin (maple) and Werner1122 (touch-me-not).

23.2 Polygamia Dioecia (“many marriages, two houses”), hermaphrodite flowers and male-only or female-only flowers occur in different plants: Gleditsia (locusts), Fraxinus (ashes), Diospyros (persimmon trees), Nyssa (tupelo), Anthospermum (anthosperm), Arctopus (bear foot), Pisonia (birdcatcher trees), Panax (ginseng).


In the order Polygamia Dioecia, Linnaeus included (from left to right, top to bottom) the honey locust (Gleditsia triacanthos), common ash (Fraxinus excelsior), American persimmon (Diospyros virginiana), water tupelo (Nyssa aquatica), bear foot (Arctopus echinatus), thorny birdcatcher tree (Pisonia aculeata) and American ginseng (Panax quinquefolius). Credits to Andrew Butko (locust), Donar Reiskoffer (ash), Dinesh Valke (persimmon), Winfried Bruenken (bear foot), Alex Popvkin (birdcatcher tree), Dan J. Pittillo (ginseng) and Flickr user lucianvenutian (tupelo).

23.3 Polygamia Trioecia (“many marriages, three houses”), there are plants with only male flowers, others with only female flowers and others with both male and female flowers: Ficus (fig trees).


The order Polygamia Trioecia included only the genus Ficus, with species such as the common fig tree (Ficus carica, left) and the sacred fig tree (Ficus religiosa, right). Credits to Flickr user INRA DIST (common fig tree) and Wikimedia user Amada44 (sacred fig tree).

By classifying all plants with flowers of different sexualities in three classes, Linnaeus made a complete mess. We usually can see at least a vague pattern toward what was later found to be phylogenetically true in some other groups, but it is hard to find anything still relevant today here.

We only need one more part and we will finally finish Linnaeus’ system!

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Linnaeus, C. (1758) Systema Naturae per regna tria Naturae…

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Filed under Botany, Systematics, taxonomy

Xenoturbella, a growing group of weirdoes

by Piter Kehoma Boll

You may never have heard of Xenoturbella, and I wouldn’t blame you. Despite being a fascinating feature of evolution, little is known about it and its magic has been hidden from most of us.

The first Xenoturbella was described in 1949 and named Xenoturbella bocki. At the time, it was considered a strange flatworm, hence its name, from Greek xenos, strange + turbella, from Turbellaria, free-living flatworms. Xenoturbella bocki is a marine animal measuring up to 3 cm in length and looking like a flat worm… a flatworm! Well, actually more like a folded worm, because its body has a series of folds running londitudinally that make it have a W shape in cross section.

Found in the cold waters around northern Europe, its body lacks a centralized nervous system, having only a net of neurons inside the epidermis. There are also no reproductive organs, neither anything similar to a kidney or any other organ beside a mouth and a gut and some structures on its surface.

For decades, X. bocki was the only species of Xenoturbella known to us. A second species was described in 1999 as X. westbladi, but molecular analyses revealed that it was the same species as X. bocki, so we continued having only one species. Thanks to molecular studies, we also figured out that Xenoturbella is not a flatworm at all, but belongs to a group of very primitive bilaterian animals, being closely related to another group of former flatworms, the acoelomorphs. Together, Xenoturbella and the acoelomorphs (a good name for a rock band, right?) form the group called Xenacoelomorpha.


Xenoturbella churro, “head” to the right. Photo by Greg Rouse.*

Forming its own phylum (or perhaps class if it is grouped in a single phylum with the acoelomorphs) named Xenoturbellida, X. bocki recently discovered that it is not alone in the world. In 2016, four new species were described from the waters of the Pacific Ocean near the coasts of Mexico and the USA, being named Xenoturbella monstrosa, X. churro, X. profunda and X. hollandorum. Considering the small size of X. bocki, some of them were monsters, especially X. monstrosa, which reaches 20 cm in length!

Four new species was quite a finding. The phylum suddenly was five times bigger than before. As someone particularly interested in obscure animal groups, especially those that once were members of the lovely phylum Plathyelminthes, I was very excited by this discovery, but I wasn’t expecting at all what happened after that.


Photo of the only known specimen of Xenoturbella japonica until now. “Head” to the left. Credits to Nakano et al. (2017).*

In December 2017, one more species was found, this time on the other side of the Pacific, near Japan. Named Xenoturbella japonica, the fifth member of the Xenoturbella genus is very welcome. The new species was based on two specimens, an adult “female” specimen (are they hermaphrodites? I don’t think we can be sure about it yet…) and a juvenile specimen. One more exciting thing is that the juvenile may actually be yet another species! But we need more material to be sure.

You can read the article describing Xenoturbella japonica here.

See also: Acoelomorpha, a phylogenetic headache

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Nakano, H.; MIyazawa, H.; Maeno, A.; Shiroishi, T.; Kakui, K.; Koyanagi, R.; Kanda, M.; Satoh, N.; Omori, A.; Kohtsuka, H. (2017) A new species of Xenoturbella from the western Pacific Ocean and the evolution of XenoturbellaBMC Evolutionary Biology17: 245.

Rouse, G.W.; Wilson N.G.; Carvajal, J.I.; Vrijenhoek, R.C. (2016) New deep-sea species of Xenoturbella and the position of Xenacoelomorpha. Nature, 530:94–7. doi:10.1038/nature16545.

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Filed under Systematics, taxonomy, worms, Zoology

The history of Systematics: Plants in Systema Naturae, 1758 (Part 7)

by Piter Kehoma Boll

We are approaching the end of the description of Linnaeus’ classification of Plants (see parts 1, 2, 3, 4, 5 and 6). Today I’ll show two more classes, the last two of plants with mainly hermaphrodite flowers.

19. Syngenesia (“same generation”)

“Husbands composed of a generative compact”, i.e., the stamens are united, forming a cylinder.

19.1 Syngenesia Polygamia Aequalis (“same generation, many equal marriages”), compound flowers formed by several small compact flowers, all having stamens and pistils: Scolymus (golden thistles), Cichorium (chicories), Catananche (cupid’s darts), Hypochaeris (cat’s ears), Andryala (andryalas), Tragopogon (goatsbeards), Picris (oxtongues), Leontodon (hawkbits and dandelions), Sonchus (sow thistles), Scorzonera (salsifies), Crepis (hawksbeards), Chondrilla (skeletonweeds), Prenanthes (rattlesnake roots), Lactuca (lettuces), Hieracium (hawkweeds), Lapsana (nippleworts), Hyoseris (hyoserises), Elephantopus (elephant’s foot), Atractylis (spindle thistles), Carlina (carline thistles), Cnicus (thistles), Arctium (burdocks), Carthamus (distaff thistles), Cynara (alcachofras), Carduus (more thistles), Onopordum (cotton thistles), Serratula (plumeless saw-worts), Echinops (globe thistles), Ageratum (whiteweeds), Cacalia (false plantains), Chrysocoma (goldenhairs), Eupatorium (thoroughworts), Santolina (cotton lavenders), Bidens (beggarticks), Staehelina (staehelinas), Stoebe (stoebes), Tarchonanthus (camphor bush).


The diverse order Syngenesia Polygamia Aequalis included (from left to right, top to bottom) the common goatsbeard (Tragopogon porrifolius), black salsify (Scorzonera hispanica), bristly oxtongue (Picris echioides, now Helminthotheca echioides), common sowthistle (Sonchus oleraceus), garden lettuce (Lactuca sativa), rush skeletonweed (Chondrilla juncea), common rattlesnake root (Prenanthes purpurea), common dandelion (Leontodon taraxacum, now Taraxacum officinale), rattlesnake hawkweed (Hieracium venosum), beaked hawksbeard (Crepis vesicaria), common andryala (Andryala integrifolia), smooth hyoseris (Hyoseris scabra), common cat’s ear (Hypochaeris radicata), common nipplewort (Lapsana communis), blue cupid’s dart (Catananche caerulea), common chicory (Cichorium intybus), Spanish golden thistle (Scolimus hispanicus), smooth elephant’s foot (Elephantopus scaber), great globe thistle (Echinops sphaerocephalus), great burdock (Arctium lappa), dyer’s plumeless saw-wort (Serratula tinctoria), musk thistle (Carduus nutans), holy thistle (Cnicus benedictus, now Centaurea benedicta), common cotton thistle (Onopordum acanthium), globe artichoke (Cynara scolymus), common carline thistle (Carlina vulgaris), common spindle thistle (Atractylus huilis), safflower (Carthamus tinctorius), common beggartick (Bidens pilosa), Alpine plantain (Cacalia alpina, now Adenostyles alpina), tall thoroughwort (Eupatorium altissimum), common whiteweed (Ageratum conyzoides), dubious staehelina (Staehelina dubia), common goldenhair (Chrysocoma coma-aurea), camphor bush (Tarchonanthus camphoratus), and common cotton lavender (Santolina chamaecyparissus). Credits to Stephen Lea (goatsbeard), H. Zell (salsify, lettuce, cotton thistle), Tony Wills (sow thistle), Radio Toreng (skeletonweed), Jane Shelby Richardson (hawkweed), Manfred Moitzi (hawksbeard), Pablo Alberto Salguero Quilles (andryala), smooth hyoseris (Hyoseris scabra), Javier Martin (hyoseris, spindle thistle), Phil Sellens (nipplewort), Isidre Blanc (cupid’s dart, staehelina), Joaquim Alves Gaspar (chicory, golden thistle, globe artichoke), Dinesh Valke (elephant’s foot), Enrico Blasutto (burdock), Kristian Peters (plumeless saw-wort), Bernd Haynold (musk thistle), Philipp Weigell (carline thistle), Vishesh Bajpai (beggartick),Benjammin Zwittnig (Alpine plantain), Frank Mayfield (thoroughwort), Peter A. Mansfeld (goldenhair), Paul Venter (camphor bush), Marie-Lan Nguyen (cotton lavender), and Wikimedia users AnemoneProjectors (oxtongue, cat’s ear), Calimo (rattlesnake root), Kropsoq (dandelion), Epp (globe thistle), 00temari (holy thistle), Pseudoanas (safflower) and Leoadec (whiteweed).*

19.2 Syngenesia Polygamia Superflua (“same generation, many remaining marriages”), compound flowers formed by several small compact flowers forming a central disk of hermaphrodite flowers surrounded by a ring of feminine flowers. Both hermaphrodite and feminine flowers are fertile and produce seeds: Tanacetum (tansies), Artemisia (artemisias), Gnaphalium (cudweeds), Xeranthemum (dry everlastings), Carpesium (carpesiums), Baccharis (baccharises), Conyza (horseweeds), Erigeron (fleabanes), Tussilago (coltsfoots), Senecio (ragworts and groundsels), Aster (asters), Solidago (goldenrods), Inula (inulas), Arnica (arnicas), Doronicum (leopard’s banes), Helenium (sneezeweeds), Bellis (daisies), Tagetes (marigolds), Zinnia (zinnias), Pectis (cinchweeds), Chrysanthemum (chrysanthemums and daisies), Matricaria (chamomiles), Cotula (water buttons), Anacyclus (anacycles), Anthemis (false chamomiles), Achillea (yarrows), Tridax (coatbuttons), Amellus (amelluses), Sigesbeckia (St. Paul’s worts), Verbesina (crownbeards), Tetragonotheca (neverays), Buphthalmum (ox-eyes).


Linnaeus put this species in the order Syngenesia Polygamia Superflua (from left to right, top to bottom): common tansy (Tanacetum vulgare), wormwood (Artemisia absinthium), heath cudweed (Gnaphalium sylvaticum), annual dry everlasting (Xeranthemum anuum), saltbush (Baccharis halimifolia), one-flower fleabane (Erigeron uniflorus), common coltsfoot (Tussilago farfara), common groundsel (Senecio vulgaris), Italian aster (Aster amellus), seaside goldenrod (Solidago sempervirens), hairy inula (Inula hirta), mountain arnica (Arnica montana), common leopard’s bane (Doronicum pardalianches), common sneezeweed (Helenium autumnale), common daisy (Bellis perennis), French marigold (Tagetes patula), Peruvian zinnia (Zinnia peruviana), Indian chrysanthemum (Chrysanthemum indicum), common chamomile (Matricaria chamomilla), buttonweed (Cotula coronopifolia), common anacycle (Anacyclus valentinus), sea false-chamomile (Anthemis maritima), common yarrow (Achillea millefolium), coatbuttons (Tridax procumbens), eastern St. Paul’s wort (Siegesbeckia orientalis), ox-eye (Buphthalmum salicifolium>). Credits to Muriel Bendel (tansy), Hermann Schachner (cudweed), Musa Geçit (dry everlasting), Bob Peterson (saltbush, coatbuttons), André Karwath (coltsfoot, daisy), C T Johansson (aster), Sam Fraser-Smith (goldenrod), Kurt Stüber (inula), Isidre Blanc (arnica), Agnieszka Kwiecien (sneezeweed), Lynda Poulter (chamomile), Walter Siegmund (buttonweed), Denis Barthel (false-chamomile), Petar Milošević (yarrow), and Wikimedia users N-Baudet (wormwood), Ghislain118 (fleabane), AnRo0002 (groundsel), Jamain (leopard’s bane, ox-eye), Rasbak (marigold), Vengolis (zinnia), Joydeep (chrysanthemum), Philmarin (anacycle) and Elouanne (St. Paul’s wort).

19.3 Syngenesia Polygamia Frustranea (“same generation, many marriages in vain”), compound flowers formed by several small compact flowers forming a central disk of hermaphrodite flowers surrounded by a ring of neutral flowers, without sexual organs, therefore only the flowers of the disk are fertile and produce seeds: Helianthus (sunflowers), Rudbeckia (black-eyed-susans), Coreopsis (coreopsises), Gorteria (gorterias), Centaurea (knapweeds), Gundelia (gundelia).


The order Syngenesia Polygamia Frustranea included (from left to right) the common sunflower (Helianthus annuus), common black-eyed susan (Rudbeckia hirta), lance-leaved coreopsis (Coreopsis lanceolata), bachelor’s button (Centaurea montana), gundelia (Gundelia tournefortii). Credits to Frank Mayfield (black-eyed susan), Jean-Pol Grandmont (bachelor’s button), Gundelia (gundelia) and Wikimedia users i_am_jim (sunflower) and KENPEI (coreopsis).*

19.4 Syngenesia Polygamia Necessaria (“same generation, many unavoidable marriages”), compound flowers formed by several small compact flowers forming a central disk of hermaphrodite flowers, but whose feminine part is sterile, surrounded by a ring of fertile feminine flowers, therefore only the flowers of the ring produce seeds: Milleria (millerias), Silphium (rosinweeds), Chrysogonum (golden knees), Melampodium (blackfoots), Calendula (pot marigolds), Arctotis (bear’s ears), Osteospermum (daisybushes), Othonna (othonnas), Polymnia (leafcups), Eriocephalus (snow bushes), Filago (cudweeds), Micropus (cotton seeds), Sphaeranthus (ballflowers).


These 7 species were included by Linnaeus in the order Syngenesia Polygamia Necessaria (from left to right, top to bottom): starry rosinweed (Silphium asteriscus), common golden knee (Chrysogonum virginianum), common pot-marigold (Calendula officinalis), whiteflower leafcup (Polymnia canadensis), Cape snow bush (Eriocephalus africanus), common cudweed (Filago germanica, now Filago vulgaris), Indian ballflower (Sphaeranthus indicus). Credits to James H. Miller (rosinweed), Fritz Flohr Reynolds (golden knee, leafcup), Wouter Hagens (pot marigold), Juanita Vilas Marchant (snow bush), Wim Rubers (cudweed), Dinnesh Valke (balflower).*

19.5 Syngenesia Monogamia (“same generation, one marriage”), stamens united forming a cylinder, but with single flowers, not forming inflorescences: Seriphium (seriphiums), Corymbium (plampers), Jasione (scabiouses), Lobelia (lobelias), Viola (violets and pansies), Impatiens (balsams).


The sheep’s scabious (Jasione montana, left), garden lobelia (Lobelia erinus, center left), common violet (Viola odorata, center right), and garden balsam (Impatiens balsamina, right) were part of the order Syngenesia Monogamia. Credits to André Karwath (lobelia), Bernard Dupont (violet) and Wikimedia users Darkone (scabious) and Joydeep (balsam).*

20. Gynandria (“female husband”)

“Husbands monstruously united to women”, i.e., flowers with stamens united to the pistils.

20.1 Gynandria Diandria (“female husband, two husbands”), two stamens united to the pistils: Orchis (orchids), Satyrium (satyre orchids), Ophrys (fly and bee orchids), Serapias (Serapis orchids), Limodorum (grass pinks), Arethusa (dragon’s mouth and snake’s mouths), Cypripedium (lady’s slippers orchids), Epidendrum (epiphytic orchids).



The order Gynandria Diandria included (from left to right, top to bottom) the military orchid (Orchis militaris), fly orchid (Ophrys insectifera), tuberous grass pink (Limodorum tuberosum, now Calopogon tuberosus), dragon’s mouth (Arethusa bulbosa), yellow lady’s slipper (Cypripedium calceolus), spathulate vanda (Epidendrum spathulatum, now Taprobanea spathulata). Credits to Holger Krisp (military orchid, fly orchid), Chris Meloche (dragon’s mouth), and Wikimedia users Algirdas (lady’s slipper) and CyberWikipedian (vanda).*

20.2 Gynandria Triandria (“female husband, three husbands”), three stamens united to the pistils: Sisyrinchium (blue-eyed grasses).

20.3 Gynandria Tetrandria (“female husband, four husbands”), four stamens united to the pistils: Nepenthes (pitcher plants).

20.4 Gynandria Pentandria (“female husband, five husbands”), five stamens united to the pistils: Ayenia (ayenias), Passiflora (passion flowers).


The common blue-eyed grass (Sisyrinchium bermudianum, left) was the only member of the order Gynandria Triandria. The distiller pitcher-plant (Nepenthes distillatoria, center) was the only member of the order Gynandria Tetrandria. The purple passion flower (Passiflora incarnata) was one of the members of the order Gynandria Pentandria. Credits to Wouter Hagens (blue-eyed grass), James & Jana Hans (pitcher-plant), Oliver P. Quillia (passion flower).*

20.5 Gynandria Hexandria (“female husband, six husbands”), six stamens united to the pistils: Aristolochia (pipevines), Pistia (water lettuce).

20.6 Gynandria Decandria (“female husband, ten husbands”), ten stamens united to the pistils: Helicteres (screw trees).


The order Gynandria Hexandria included the smearwort (Aristolochia rotunda, left) and the water lettuce (Pistia stratiotes, center). The order Gynandria Decandria included the Indian screw tree (Helicteres isora, right). Credits to J. M. Garg (screw tree) and Wikimedia users Hectonichus (smearwort) and Keisotyo (water lettuce).*

20.7 Gynandria Polyandria (“female husband, many husbands”), many stamens united to the pistils: Xylopia (xylopias), Grewia (crossberries), Arum (arums), Dracontium (arum yams), Calla (callas), Pothos (pothos), Zostera (eelgrasses).


The order Gynandria Polyandria included (from left to right) the crossberry (Grewia occidentalis), dragon arum (Arum dracunculus, now Dracunculus vulgaris), elephant-foot yam (Dracontium polyphyllum, now Amorphophallus paeoniifolius), wild calla (Calla palustris) and climbing pothos (Pothos scandens). Credits to P. Pickaert (arum), Kurt Stüber (calla), and Wikimedia users Consultaplantas (crossberry), Fotokannan (yam) and Vinayaraj (pothos).*

As you can see, the class Syngenesia is much more regular than the class Gynandria. Most species of Syngenesia are currently included in the family Asteraceae. Gynandria, on the other hand, includes a variety of unrelated plants, including orchids, arum plants and even passion flowers!

Here we finish all plants with hermaphroditic flowers. We only need two more posts and we will have seen the whole system of Linnaeus!

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Linnaeus, C. (1758) Systema Naturae per regna tria Naturae…

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Filed under Botany, Systematics, taxonomy

The hammerhead flatworms: once a mess, now even messier

by Piter Kehoma Boll

Few people know that land planarians exist, but when they do, they most likely know the hammerhead flatworms, which comprise the subfamily Bipaliinae.

The hammerhead flatworms, or simply hammerhead worms, have this name because their head has lateral expansions that make them resemble a hammer, a shovel or a pickaxe. Take a look:


The “wandering hammerhead worm”, Bipalium vagum. Notice the peculiar head. Photo by flickr user budak.*

The Chinese knew the hammerhead worms at least since the 10th century, which is understandable, since they are distributed from Japan to Madagascar, including all southern and southeast Asia, as well as Indonesia, the Philippines and other archipelagos. The western world, however, first heard of them in 1857, when William Stimpson described the first species and put them in a genus called Bipalium, from Latin bi- (two) + pala (shovel), due to the head shape. One of them was the species Bipalium fuscatum, a Japanese species that is currently considered the type species of the genus.


Anterior region of Bipalium fuscatum, the “brownish hammerhead worm”. Photo by Wikimedia user 根川大橋.**

Two years later, in 1859, Ludwig K. Schmarda described one more species, this one from Sri Lanka, and, unaware of Stimpson’s paper, called the species Sphyrocephalus dendrophilus, erecting the new genus for it from Greek sphȳra (hammer) + kephalē (head).


Drawings by Schmarda of Sphyrocephalus dendrophilus.

In the next year, 1860, Edward P. Wright did something similar and described some hammerhead worms from India and China, creating a new genus, Dunlopea, for them. The name was a homage to his friend A. Dunlop (whoever he was).


Wright’s Drawing of Dunlopea grayia (now Diversibipalium grayi) from China.

Eventually those errors were perceived and all species were put in the genus Bipalium, along with several others described in the following years. All hammerhead worms were part of the genus Bipalium until 1896, when Ludwig von Graff decided to improve the classification and divided them into three genera:

1. Bipalium: With a head having long “ears”, a well developed head.
2. Placocephalus (“plate head”): With a more semicircular head.
3. Perocephalus (“mutilated head”): With a shorter, rudimentary head, almost as if it had been cut off.


Compare the heads of typical species of Bipalium (left), Placocephalus (center) and Perocephalus (right), according to Graff.

This system, however, was soon abandoned and everything went back to be simply Bipalium and continued that way for almost a century, changing again only in 1998, when Kawakatsu and his friends started to mess with the penises of the hammerhead worms.

First, in 1998, they erected the genus Novibipalium (“new Bipalium“) for species with a reduced or absent penis papilla, and retained in Bipalium those with a “well”-developed penis papilla. It is worth noticing though that this well-developed papilla is not much bigger than a reduced papilla in Novibipalium. In both genera the actual, functional penis is formed by a set of folds in the male atrium and not by the penis papilla itself as in other land planarians that have a penis papilla.

Later, in 2001, Ogren & Sluys separated some more species of Bipalium in a new genus called Humbertium (after Aloïs Humbert, who described most species of this new genus). They were separated from Bipalium because the ovovitelloducts (the ducts that conduct the eggs and vitellocites) enter the female atrium from ahead, and not from behind as in the typical Bipalium. This separation is, in my opinion, more reasonable than the previous one.

Now we had three genera of hammerhead worms based on their internal anatomy, but several species were described without any knowledge of their sexual organs. Thus, in 2002, Kawakatsu and his friends created one more genus, Diversibipalium (the “diverse Bipalium“) to include all species whose anatomy of the sexual organs was unknown. In other words, it is a “wastebasket” genus to place them until they are better studied.

Are these three genera, Bipalium, Novibipalium and Humbertium, as now defined, natural? We still don’t know, but I bet they are not. A good way to check it would be by using molecular phylogeny, but we don’t have people working with these animals in their natural habitats, so we do not have available material for that. Another thing that can give us a hint is to look at their geographical distribution. We can assume that genetically similar species, especially of organisms with such a low dispersal ability as land planarians, all occur in the same geographical region, right? So where do we find species of each genus? Let’s see:

Bipalium: Indonesia, Japan, China, Korea, India.

Novibipalium: Japan.

Humbertium: Madagascar, Sri Lanka, Southern India, Indonesia.

Weird, right? They are completely mixed and covering a huge area of the planet, especially when we consider Humbertium. We can see a tendency, but nothing very clear.

Fortunately, some molecular analyses were published (see Mazza et al. (2016) in the references). One, which included the species Bipalium kewense, B. nobile, B. adventitium, Novibipalium venosum and Diversibipalium multilineatum placed Diversibipalium multilineatum very close to Bipalium nobile, and they are in fact very similar, so I guess that we can transfer it from Diversibipalium to Bipalium, right? Similary, Novibipalium venosum appears mixed with the species of Bipalium. I guess this is kind of messing things up one more time.


Head of some species of Bipalium, including the ones used in the study cited above. Unfortunately, I couldn’t find a photo or drawing of Novibipalium venosum. Image by myself, Piter Kehoma Boll.**

Interestingly, among the analyzed species, the most divergent was Bipalium adventitium, whose head is “blunter” than that of the other ones. Could the head be the answer, afterall? Let’s hope that someone with the necessary resources is willing to solve this mess soon.

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See also:

Once found and then forgotten: the not-so-bright side of taxonomy.

The lack of taxonomists and its consequences on ecology.

They only care if you are cute. How charisma harms biodiversity.

The faboulous taxonomic adventure of the genus Geoplana.

Darwin’s Planaria elegans: hidden, extinct or misidentified?

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Graff, L. v. (1896) Über das System und die geographische Verbreitung der Landplanarien. Verhandlungen der Deutschen Zoologischen Gesellschaft6: 61–75.

Graff, L. v. (1899) Monographie der Turbellarien. II. Tricladida Terricola (Landplanarien). Engelmann, Leipzig.

Kawakatsu, M.; Ogren, R. E.; Froehlich, E. M. (1998) The taxonomic revision of several homonyms in the genus Bipalium, family Bipaliidae (Turbellaria, Seriata, Tricladida, Terricola). The Bulletin of Fuji Women’s College Series 236: 83–93.

Kawakatsu, M.; Ogren, R. E.; Froehlich, E. M., Sasaki, G.-Y. (2002) Additions and corrections of the previous land planarians indices of the world (Turbellaria, Seriata, Tricladida, Terricola). The bulletin of Fuji Women’s University. Ser. II40: 162–177.

Mazza, G.; Menchetti, M.; Sluys, R.; Solà, E.; Riutort, M.; Tricarico, E.; Justine, J.-L.; Cavigioli, L.; Mori, E. (2016) First report of the land planarian Diversibipalium multilineatum (Makino & Shirasawa, 1983) (Platyhelminthes, Tricladida, Continenticola) in Europe. Zootaxa4067(5): 577–580.

Ogren, R. E.; Sluys, R. (2001) The genus Humbertium gen. nov., a new taxon of the land planarian family Bipaliidae (Tricladida, Terricola). Belgian Journal of Zoology131: 201–204.

Schmarda, L. K. (1859) Neue Wirbellose Thiere beobachtet und gesammelt auf einer Reise um die Erde 1853 bis 1857 1. Turbellarien, Rotatorien und Anneliden. Erste Hälfte. Wilhelm Engelmann, Leipzig.

Stimpson, W. (1857) Prodromus descriptionis animalium evertebratorum quæ in Expeditione ad Oceanum, Pacificum Septentrionalem a Republica Federata missa, Johanne Rodgers Duce, observavit er descripsit. Pars I. Turbellaria Dendrocœla. Proceedings of the Academy of Natural Sciences of Philadelphia9: 19–31.

Wright, E. P. (1860) Notes on Dunlopea. Annals and Magazine of Natural History, 3rd ser.6: 54–56.

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Filed under flatworms, Systematics, taxonomy, worms, Zoology