Tag Archives: synapsid

Know Your Bones: June 2015

Last month’s challenge was a stumper. For most of the month, only one person dared to give a guess. Nevertheless, it was not until days before the month ended that Isotelus came in with the correct answer.


The Dicynodont Placerias hesternus


This critter is indeed Placerias hesternus.


 photo 2015-06-05 09.36.01_zps3si6xnjp.jpg

(Taken at the New Mexico Museum of Natural History and Science)


Placerias lived during the late Triassic 221 to 210 million years ago. Placerias would have reached a length of ~3.5 meters and weighed in at nearly 1000 kilograms, making it one of the largest herbivores known about during this time. It was also one of the most common animals around during the late Triassic. Placerias had a beak and two tusks, which are common traits for dicynodonts. Both males and females had the same size tusks, thus they would have most likely used them in obtaining food and defense; not necessarily in finding mates. It is thought that Placerias would have had a life style similar to modern hippopotamuses, wallowing in semi-shallow rivers and lakes and spending little time outside of water.


 photo 2015-06-05 09.36.59_zps7guvthxk.jpg

(Taken at the New Mexico Museum of Natural History and Science)


Even though Placerias lived during the “Age of Dinosaurs” (the Mesozoic), it was not a dinosaur, it is a synapsid. Along with being a synapsid, it is also a therapsid, meaning it is very closely related to modern mammals, but falls outside of the modern mammal clade. Fossil animals, such as Placerias, are found across the world and were key evidence to help establish that at one time in earth’s past, all the continents were of one land mass (Pangaea). Dicynodonts are the second most successful synapsid clade and are only surpassed by mammals in their diversity and longevity.


Moving on to next month’s challenge:


 photo Dayatthemuseum036_zpsb8b3d5b6.jpg

(Taken at the New Mexico Museum of Natural History and Science)


Since last month’s was so difficult, I am hoping this one is much easier.

Know Your Bones: January 2014

Last month’s challenge was very easy. It was so easy that duclicsic posted a correct answer within minutes of the blog going up. However, later in the month Aught3 posted an even more correct answer:


Dimetrodon limbatus

Reason: Google-fu


This is a specimen of Dimetrodon and Aught3 is even more correct in that it is specifically Dimetrodon limbatus.


 (Taken at the New Mexico Museum of Natural History and Science)

Dimetrodons inhabited the earth 295 – 272 million years ago, during the Permian. Dimetrodons were most likely the top predator on earth during that time. The most prominent feature of Dimetrodon is the sail on its back. The sail was most likely used as a heat regulator, but some scientists have suggested that it might be an example of sexual selection, similar to the Peacock’s tail. Either way, the sail on its back and four-legged posture makes Dimetrodon one of the easiest prehistoric critters to identify.


There is confusion about Dimetrodon, in that several people believe that it was a dinosaur, I think this is because Dimetrodons are always found in Prehistoric Play Sets and most people believe dinosaurs were just big lizards. Dimetrodon does resemble a large lizard with a sail on its back. However, there are three main reasons Dimetrodon was not a dinosaur; the first most obvious one is that it is much older than any dinosaur. The second is the sprawling, lizard-like stance of its legs. Dinosaurs’ legs, unlike lizards, are directly under their bodies and not protruding from the side of the body like modern lizards. The third is that Dimetrodon is actually more closely related to modern mammals than it is to reptiles such as dinosaurs.


Dimetrodon belongs to the synapsid clade along with all mammals. This means that behind the eye, there is only one hole for muscle attachments. Dinosaurs belong to the diapsid clade, meaning they have two holes behind the eye for muscle attachments.


Moving on to this months challenge:


 (Taken at the Dinosaur Museum and Natural Science Laboratory)

Good luck and happy 2014.