#silesauridae

So, in the midst of the thousand thousand other projects I have started, on this website and in life…I just wanna have some fun with art. Not the best artist, so forgive my trespasses here, especially with a dinosaur species I’ve, admittedly, never heard of! Neat one, though! This is a part of the #DrawDinosDaily challenge posted by @a-dinosaur-a-day, so I’ll try and do as many of these as I can this month (or…year?)!

So, middle Triassic dinosaur known from fossils in Tanzania, which is super neat! He’s kind of a weirdy, with longer front limbs, functional fifth toes, a toothless front of the mouth, and an unclear phylogenetic relationship to a primitive group of the dinosaurs, the silesaurids. I skimmed a few papers (unaccustomed to reading paleontological species description papers, so that was a lot of jargon), got some vibe of the guy, and put him to paper! Or iPad.

The potential inaccuracies in my depiction are the implications of feathers (no direct evidence, especially for a dinosaur this old, but there is some academic speculation that feathers may be this early), the way the feet are drawn (that was a lot harder than I thought it would be, but I think I got that functional fifth toe right in there), and the length of the front limbs (they ARE long, but I leant into some older interpretations of the species). So, to my fellow dinosaur lovers, sorry about that! Been a while since I’ve drawn a non-avian dinosaur, and certainly not in this style. Hopefully, sticking with this challenge helps me improve a bit! Next up, the Bearded Reedling (Panurus biarnicus)!

Pisanosaurus mertii (as a silesaurid)

Last week I mentioned the one oddball dinosauriform that had crocodilian-like osteoderm armor, so let's take a look at that one too.

Lewisuchus admixtus lived in what is now northwest Argentina during the late Triassic, around 236-234 million years ago. About 1m long (3'3"), it was an early member of the silesaurids – a group of dinosauriforms that weren't quite dinosaurs themselves, but were very closely related to the earliest true dinosaurs.

(They've also been proposed as instead being early ornithisichians, but we're not getting into that today.)

Much like its later silesaurid relatives Lewisuchus had a long neck and slender limbs, and was probably mainly quadrupedal, possibly with the ability to briefly run bipedally to escape from threats. Its serrated teeth suggest it was carnivorous, likely feeding on both smaller vertebrates and the abundant insects found in the same fossil beds.

Uniquely for an early dinosauriform it also had a single row of bony osteoderms running along its spine. Although it lived at close to the same time as the similarly-armored Mambachiton their last common ancestor was at least 10 million years earlier, and no other early dinosaur precursors with osteoderms are currently known – so this was probably a case of Lewisuchus independently re-evolving the same sort of feature.

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Portrait of dinosauromorph Pisanosaurus mertii from the Late Triassic of Argentina. A partial skeleton of this reptile was discovered in rocks of the Ischigualasto Formation and described in 1967 as belonging to a basal ornithischian. Initially, the animal was even attributed to the Pisanosauridae family. Phylogenetic analyses in 2015 and subsequent years showed it as a relative or even a representative of silesaurids, a group of dinosaurs very close to dinosaurs proper. Pisanosaurus has features of both silesaurids and early ornithischians, which may indicate the relationship of these groups. Judging by the single specimen, it reached a little over a meter in length. The animal's name was given in honor of paleontologist Juan Arnaldo Pisano.

I decided to make a portrait because, due to the uncertain classification, it is not known whether Pisanosaurus was bipedal or quadrupedal. Filamentous structures are speculative.

Silesaurus opolensis here was a type of dinosauriform – a reptile very closely related to the ancestors of true dinosaurs, but not quite actually a dinosaur itself.

Living in Poland during the Late Triassic (~230 million years ago), it was a quadrupedal animal roughly the size of a large modern dog, about 50cm tall at the shoulder (1'8") and 2m long (6'6"). The front of its lower jaw was toothless and covered with a keratinous beak, and there may have been a corresponding much smaller beak at the very tip of its upper jaw, too.

It was originally thought to be a herbivore, but coprolites full of insect remains suggest it was probably more of an omnivore, possibly foraging by pecking in a convergently similar manner to its distant bird cousins.

In fact, one of those pieces of Silesaurus poop was recently found to preserve a new species of tiny beetle in incredible detail.

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Pisanosaurus mertii from the Late Triassic of Argentina (~228-216 mya).

Known only from a partial skull and a few pieces of its skeleton, this 1m long animal (3′3″) is usually considered to the be the earliest known member of the ornithischian dinosaurs -- but some recent studies have thrown that into question, suggesting that it might not even be a dinosaur at all.

Instead it may have been a member of the silesaurids, Triassic dinosauriforms that were close cousins to the dinosaurs but not quite true members of the group. Small and lightly-built, silesaurids had long front limbs and may have been at least partially quadrupedal, and some showed evidence of herbivory with beaks at the tips of their snouts.