Author Archives: Piter Keo

About Piter Keo

I'm a biology student, currently working with land planarians. I love biology, astronomy, languages and mythology, among other things.

Shaking dinosaur hips and messing with their heads

by Piter Kehoma Boll

This week brought astonishing news regarding the phylogeny of dinosaurus, as you perhaps have heard or read. New anatomical evidences have completely rebuilt the basis of the dinosaur family tree and I’m here to explain a little bit of what happened.

As we all know, Dinosaurs include a great variety of beasts, from the meat-eating theropods to the long-necked sauropods and from the horned ceratopsians to the armored ankylosaurs, among many others.

largestdinosaursbysuborder_scale

Silhouette of a human compared to the largest known dinosaurs of each major group. Picture by Matt Martyniuk.*

For more than a century now, dinosaurus have been divided into two groups, called Ornithischia and Saurischia. Ornithischia (“bird-hipped”) includes dinosaurus whose pelvic bones are more similar to what is found in birds, with a pubis directed backward. Saurischia (“lizard-hipped”), on the other hand, have a pubis directed forward, as in reptiles in general. This grouped the theropods and the sauropods in the same group as Saurischia while other dinosaurus were grouped as Ornithischia. But birds are actually theropods, thus being lizard-hipped dinosaurus and not bird-hipped dinosaurus! Confusing, isn’t it? So let’s take a look at their hips:

Pelvic_bones

Comparison of the hips of a crocodile (Crocodylus), a sauropod (Diplodocus), a non-avian theropod (Tyrannosaurus), a bird (Apteryx), a thyreophoran (Stegosaurus), and an ornithopod (Iguanodon). Red = pubis; Blue = ischium; Yellow = ilium. Picture by myself, Piter K. Boll.**

As you can see, the primitive state, found in crocodiles, sauropods and early theropods, is a pubis pointing forward. A backward-pointing pubis evolved at least twice independently, both in more advanced theropods (such as birds) and the ornithischian dinosaurus. But could we be so certain that Tyrannosaurus and Diplodocus are more closely related to each other (forming a clade Saurischia) just because of their hips? Afterall, this is a primitive hip, so it is very unlikely to be a synapomorphy (a shared derived character). Nevertheless, it continued to be used as a character uniting sauropods and theropods.

A new paper published by Nature this week, however, showed new evidences that point to a different relationship of the groups. After a detailed analysis of the bone anatomy, Matthew G. Baron, David B. Norman and Paul M. Barrett have found 20 characters that unite theropods with ornithischians and not with sauropods. Among those we can mention the presence of a foramen (a hole) at the anterior region of the premaxillary bone that is inside the narial fossa (the depression of the bone that surrounds the nostril’s opening) and a sharp longitudinal ridge along the maxilla.

skulls

The skulls of both ornithischians and theropods (above) show an anterior premaxillary foramen in the narial fossa (shown in yellow) and and a sharp ridge on the maxilla (shown in green), as well as other characters that are not present in sauropodomorphs and herrerasaurids (below). Composition using original pictures by Carol Abraczinskas and Paul C. Sereno (Heterodontosaurus), Wikimedia user Ghedoghedo (Eoraptor and Herrerasaurus), and flickr user philosophygeek (Plateosaurus).**

In his blog Tetrapod Zoology, Dr. Darren Naish comments the new classification and points out some problems that arise with this new view. One of them is the fact that both theropods and sauropodomorphs have pneumatic (hollow) bones, while ornithischians do not. If the new phylogeny is closer to the truth, that means that pneumacity evolved twice independently or evolved once and was lost in ornithischians.

He also mentions that both ornithischians and theropods had hair-like or quill-like structures on their skin. In theropods this eventually led to feathers. Could this be another synapomorphy uniting these groups? Maybe… but when we think that pterosaurs also had “hairs”, one could also conclude that a “hairy” integumentary structure was already presented in the common ancestor of dinosaurus. In this case, perhaps, we only had not found it yet on sauropods. Now imagine a giant Argentinosaurus covered with feathers!

One concern that appeared with this new organization is whether sauropodomorphs would still be considered dinosaurs. The term “dinosaur” was coined by Richard Owen in 1842 to refer to the remains of the three genera known at the time, Iguanodon, Hylaeosaurus and Megalosaurus, the first two being ornithischians and the latter a theropod. As a consequence, the original definition of dinosaur did not include sauropods. Similarly, the modern phylogenetic definition of dinosaur was “the least inclusive clade containing Passer domesticus (the house sparrow) and Triceratops horridus“. In order to allow Brachiosaurus and his friends to continue sitting  with the dinosaurs, Baron et al. suggested to expand the definition to include Diplodocus carnegii. So, dinosaurus would be the least inclusive clade containing P. domesticusT. horridus and D. carnegii.

In this new family tree, the name Saurischia would still be used, but to refer only to the sauropodomorphs and some primitive carnivores, the herrerasaurids. The new clade formed by uniting theropods and ornithischians was proposed to be called Ornithoscelida (“bird-legged”), a name coined in 1870 to refer to the bird-like hindlimbs of both theropods and ornithopods (the subgroup of ornithischians that includes dinosaurs such as Iguanodon and the duck-billed dinosaurs).

What can we conclude with all that? Nothing will change if you are just a dinosaur enthusiast and do not care about what’s an ornithischian and a saurischian. Now if you are a phylogeny fan, as I am, you are used to sudden changes in the branches. Most fossils of basal dinosaurs are incomplete, thus increasing the problem to know how they are related to each other. Perhaps this new view will last, perhaps new evidence will change all over again the next week.

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ResearchBlogging.orgReferences and further reading:

Baron, M., Norman, D., & Barrett, P. (2017). A new hypothesis of dinosaur relationships and early dinosaur evolution Nature, 543 (7646), 501-506 DOI: 10.1038/nature21700

Naish, D. (2017). Ornithoscelida Rises: A New Family Tree for DinosaursTetrapod Zoology.

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Friday Fellow: Divergent Dinobryon

by Piter Kehoma Boll

Let’s return once more to the troublesome and neglected protists. This time I’m bringing you another tiny but beautiful alga, more precisely a golden alga. Its name is Dinobryon divergens and as usual there is no common name, so I invented one by simply translating the scientific name, thus I’ll call it the divergent dinobryon.

The divergent dinobryon is part of the class Chrysophyceae, commonly known as golden algae. Measuring about 50 µm in length, it lives in temperate lakes around the world and forms colonies composed of about 6 to 50 ovoid cells that are surrounded by a vase-like shell (lorica) of cellulose, as seen in the picture below.

dinobryon_divergens

A branching colony of Dinobryon divergens. The cells are clearly visible inside the lorica. Photo by Frank Fox.*

During colony formation, an original cell divides and one of the two daughter cells slides to the opening of the lorica and starts to construct a new one. It starts by creating the base of the lorica, which has a funnel shape and is attached to the inner wall of the original lorica. With further divisions, the colony starts to grow in a tree-like form. And the most interesting part is that the cells have two flagella and use them to swim, pulling the whole colony through the water.

As with other golden algae, the divergent dinobryon produces an internal siliceous structure that is globose, hollow and has a single opening connecting to the outside. This structure is called a statospore or stomatocyst and allows the cell to enter a resting state (cyst). The statospore is an important structure to help distinguish different species of golden algae.

The divergent dinobryon is a mixotrophic organism, meaning that it feeds by photosynthesis and by ingesting food too, especially bacteria. Kind of an interesting fellow, don’t you think?

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ResearchBlogging.orgReferences:

Franke, W., & Herth, W. (1973). Cell and lorica fine structure of the chrysomonad alga, Dinobryon sertularia Ehr. (Chrysophyceae) Archiv für Mikrobiologie, 91 (4), 323-344 DOI: 10.1007/BF00425052

Herth, W. (1979). Behaviour of the chrysoflagellate alga, Dinobryon divergens, during lorica formation Protoplasma, 100 (3-4), 345-351 DOI: 10.1007/BF01279321

Karim, A., & Round, F. (1967). Microfibrils in the lorica of the freshwater alga Dinobryon New Phytologist, 66 (3), 409-412 DOI: 10.1111/j.1469-8137.1967.tb06020.x

Sandgren, C. (1981). Characteristics of sexual and asexual resting cyst (statospore) formation in Dinobryon cylindricum Imhof (Chrysophyta) Journal of Phycology, 17 (2), 199-210 DOI: 10.1111/j.1529-8817.1981.tb00840.x

Sheath, R., Hellebust, J., & Sawa, T. (1975). The statospore of Dinobryon divergens Imhof: Formation and germination in a subarctic lake Journal of Phycology, 11 (2), 131-138 DOI: 10.1111/j.1529-8817.1975.tb02760.x

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New Species: March 11 to 20, 2017

by Piter Kehoma Boll

Here is a list of species described from March 11 to March 20. It certainly does not include all described species. Most information comes from the journals Mycokeys, Phytokeys, Zookeys, Phytotaxa, Zootaxa, International Journal of Systematic and Evolutionary Microbiology, and Systematic and Applied Microbiology, as well as journals restricted to certain taxa.

Cherax_warsamsonicus

Cherax warsamsonicus is a new crayfish from Indonesia.

SARs

Plants

Fungi

Flatworms

Annelids

Rotifers

Tardigrades

Arachnids

Myriapods

Crustaceans

Insects

Cartilaginous fishes

Ray-finned fishes

Lissamphibians

Reptiles

Mammals

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Friday Fellow: Pliable Brachionus

by Piter Kehoma Boll

Charles Darwin had already noticed that small animals, such as those found in zooplankton, are widely distributed around the world, even those that are found in small ponds of freshwater. This seemed to go against the speciation theories, but it was thought to be the result of passive transport by other animals, such as migratory birds. One of such species is the tiny rotifer Brachionus plicatilis, or the pliable brachionus, as I decided to call it, a 0.1 to 0.2 mm long species found worlwide in saline lakes.

brachionus_plicatilis

A specimen of the pliable brachionus. Photo by Wikimedia user Sofdrakou.*

The pliable brachionus is a euryhaline species, meaning it can tolerate a wide range of salinity. Recent molecular studies have shown that it is actually a complex of at least 22 different species, but as this was not yet taxonomically defined, I will continue to use the terms Brachionus plicatilis and plicate brachionus in the broad sense.

In the last half century, the pliable brachionus became a commercially important species, being raised as a food source for fish larvae. It may be fed with a variety of microorganisms, such as bacteria, algae and yeasts. In the natural environment, it is considered a generalist filter-feeding species.

As many rotifers, the pliable brachionus usually reproduces by parthenogenesis, where the so-called amictic females produce diploid eggs that originate other amictic females. Under certain conditions, however, they may produce eggs that originate mictic females, which only lay haploid eggs. Unfertilized haploid eggs originate males, while those that are fertilized originate new females. A bit complex, right?

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ResearchBlogging.orgReferences:

Gómez, A., Serra, M., Carvalho, G., & Lunt, D. (2002). Speciation in ancient cryptic species complexes: evidence from the molecular phylogeny of Brachionus plicatilis(Rotifera) Evolution, 56 (7) DOI: 10.1554/0014-3820(2002)056[1431:SIACSC]2.0.CO;2

Øie, G., Makridis, P., Reitan, K., & Olsen, Y. (1997). Protein and carbon utilization of rotifers (Brachionus plicatilis) in first feeding of turbot larvae (Scophthalmus maximus L.) Aquaculture, 153 (1-2), 103-122 DOI: 10.1016/S0044-8486(96)01514-1

Suatoni, E., Vicario, S., Rice, S., Snell, T., & Caccone, A. (2006). An analysis of species boundaries and biogeographic patterns in a cryptic species complex: The rotifer—Brachionus plicatilis Molecular Phylogenetics and Evolution, 41 (1), 86-98 DOI: 10.1016/j.ympev.2006.04.025

Walker, K. (1981). 13. A synopsis of ecological information on the saline lake rotifer Brachionus plicatilis Müller 1786 Hydrobiologia, 81-82 (1), 159-167 DOI: 10.1007/BF00048713

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Badass females are unpopular among praying mantids

by Piter Kehoma Boll

One of the most iconic representations of praying mantids is that of a female eating the male after (or during) sex, an unpleasant scenario that starts with a beheading before the poor male even finishes his job.

Mantismeal

Delicious male meal. Photo by Wikimedia user Classiccardinal.*

According to some studies, when the male is beheaded, he increases the pumping of semen into the female, thus increasing the chances of fecundation. This could make one think that being eaten is actually an advantage to the male, as it makes him have more offspring.

Several observations with different species show the opposite though. Males make everything they can to avoid being eaten by the female, as it allows them to copulate with additional females. But how can they escape from such a gruesome destiny?

It is known that hungry females are more eager to eat the partner than satiated ones. Well-fed females (fat ones) are also less likely to have a meal in bed than malnourished ones. Males can tell whether a female is hungry or malnourished and thus avoid those in such conditions. They like fat and fed females. But this is not the only thing that males take into account when choosing the appropriate mother for their children.

A study from 2015 by researchers of the University of Buenos Aires have shown that males of the species Parastagmatoptera tessellata, found in South America, also choose females based on their personality.

In a laboratory experiment, a male was put in a container where he could see two females, one aggressive and one non-aggressive. Another male was presented to both females (which were unable to see each other) and the aggressive female always attacked the male, while the non-aggressive one never did. After watching how each female behaved, the male received access to both and could choose his favorite one.

And guess what? The non-aggressive one was chosen most of the time. This means that males are not only able to tell whether they are likely to be eaten based on the female’s hunger and nutritional condition, but also by analyzing the behavior of the female towards other males.

See also:

Gender conflict: Who’s the man in the relationship?

Male dragonflies are not as violent as thought

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ResearchBlogging.orgReferences:

Lelito, J., & Brown, W. (2008). Mate attraction by females in a sexually cannibalistic praying mantis Behavioral Ecology and Sociobiology, 63 (2), 313-320 DOI: 10.1007/s00265-008-0663-8

Scardamaglia, R., Fosacheca, S., & Pompilio, L. (2015). Sexual conflict in a sexually cannibalistic praying mantid: males prefer low-risk over high-risk females Animal Behaviour, 99, 9-14 DOI: 10.1016/j.anbehav.2014.10.013

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Filed under Behavior, Entomology, Zoology

New Species: March 1 to 10

by Piter Kehoma Boll

Here is a list of species described from March 1 to March 10. It certainly does not include all described species. Most information comes from the journals Mycokeys, Phytokeys, Zookeys, Phytotaxa, Zootaxa, International Journal of Systematic and Evolutionary Microbiology, and Systematic and Applied Microbiology, as well as journals restricted to certain taxa.

Pristimantis_attenboroughi

Pristimantis attenboroughi is a new frog species described in the past 10 days and named in honor of Sir David Attenborough.

SARs

Plants

Fungi

Sponges

Entoprocts

Annelids

Kinorhynchs

Nematomorphs

Nematodes

Arachnids

Myriapods

Crustaceans

Hexapods

Ray-finned fishes

Lissamphibians

Reptiles

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Friday Fellow: Tree Tumbo

by Piter Kehoma Boll

Today I’m introducing one of the most bizarre plant species in the world. Found in the Namib desert, in Namibia and Angola, the Welwitschia mirabilis, usually simply called welwitschia or tree tumbo in English, is the solely member of the order Welwitschiales, a group of gymnosperms in the division Gnetophyta.

welwitschia_mirabilis

A specimen of Welwitschia mirabilis in Naukluft, Namibia. Photo by Sara&Joachim*

The tree tumbo has a unique appearance. The seedlings have two cotyledons (the original leaves produced by the seed) and later develop two permanent leaves that grow opposite (at right angles) to the cotyledons. These permanent leaves grow continuosly, reaching up to 4 m in length. While growing, the leaves split and fray into several straps and occupy an area of about 8 m in circunference around the plant. The stem is woody and the flowers appear on a central part called crown. The species is dioecious, meaning that male and female flowers appear in different plants. Pollination is usually carried out by insects.

Living up to 2 thousand years, the tree tumbo is a very peculiar desert plant. Its leaves are broad and very large, different from what is the rule in the desert. Its root system is also very shallow, not penetrating deep in the ground. It seems that most of the water used by the plant is captured by the leaves from the morning fog.

Although having a very restrict range, the tree tumbo is not (yet) and endangered plant, as its population is considerably large. However, due to its popularity, some areas attract collectors, and since its growth is so slow, it may eventually become a vulnerable plant.

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References:

Bornmann, C. H. 1972. Welwitschia mirabilis: paradox of the Namib Desert. Edeavour, 31(113):95–99.

Wikipedia. Welwitschia mirabilis. Available at <https://en.wikipedia.org/wiki/Welwitschia&gt;. Access on March 1, 2017.

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