Nearly quarter of a billion year old pterosaur predecessor identified in Scotland

[rogue06]

Not a new discovery itself but rather a reassessment of one discovered over a century ago, back in 1907, of a tiny creature, classed as a archosauriform, that lived some time between 240 and 210 mya (Late Triassic).

The creature in question was named Scleromochlus taylori was 18cm (7.1") long, and while it didn't leave any fossilized bones or other bits, the partial skeletons of seven individuals preserved as an impression was left in the Carnian Lossiemouth Sandstone of northeastern Scotland. This natural mold, which is of so-so quality, doesn't include part of its skull or its tail, and reveals that Scleromochlus' body was rather gracile and it possessed long hind legs, a short neck and large head.

But where Scleromochlus belonged in the phylogenetic "tree of life" was a matter of debate with one side declaring it was a close relative of the dinosaurs, while the other side argued it was a forerunner of the pterosaurs -- winged reptiles, the first animals with bones to take to the skies.

This is where a team of researchers headed by Davide Foffa of the Department of Natural Sciences at National Museums Scotland and the University of Birmingham's School of Geography, Earth and Environmental Sciences, steps in, hoping to finally resolve the issue by using computed tomography (CT) scans.

The new images revealed the creature in unprecedented detail, permitting the team to describe new features, such as the shape of the upper jaw and thigh bones. As palaeontologist and co-author Paul M. Barrett of London's Natural History Museum explained, the CT scans allowed them to finally see tiny bones still encased in the rock and to digitally fill in the voids in the sandstone to create accurate virtual models of Scleromochlus.

The scans revealed that it lacks adaptations for flying, arboreality (animals living in trees), or leaping (the latter was one of the most recent theories), but that Scleromochlus were more closely related to pterosaurs than to dinosaurs based largely on the structure of the femur particularly the bottom where it connected to the lower leg, in that it bears a structure that is a hallmark of lagerpetids. This family of reptiles has been recently recognized as being very closely related and part of a group collectively called pterosauromorphs.

They figure that Scleromochlus was likely a lagerpetids and showed characteristics of both it and pterosauromorphs.

But while this may end the debate over Scleromochlus, it still remains unclear how ground-based reptiles like this evolved into soaring pterosaurs roughly 10 to 15 million years later since there aren't any fossils of reptiles that had taken steps towards an airborne life, but were not yet fully-fledged fliers. The record goes from creatures such as Scleromochlus to pterosaurs completely adapted for flying.

As Foffa puts it, "We do not have an animal that is in between lagerpetids and pterosaurs, which is frustrating, but I hope that at least we are providing some extra information on what these animals would look like."

Source: Fossils Reveal Pterosaur Relatives Before They Evolved Wings

By reanalyzing earlier specimens, scientists linked small, leggy creatures that roamed 237 million years ago to the reptiles that flew through the dinosaur era.



Few creatures were built to soar like pterosaurs. Tens of millions of years before the earliest birds, these Mesozoic reptiles had pioneered flight with sail-shaped wings and lightweight bones. Eventually pterosaurs the size of small planes would take to the sky, pushing the boundaries of animal aviation.

But the origins of these reptiles have remained murky because of a lack of fossils from the earliest fliers. “The oldest pterosaur we have already had wings and were capable fliers,” said Davide Foffa, a paleontologist at Virginia Tech, which makes it difficult to chart their aerial evolution.

For decades, paleontologists have postulated that the earliest pterosaurs dwelled in trees and experimented with gliding before flying. But Dr. Foffa and his colleagues may have discovered a more ground-bound origin for these ancient aviators. In a study published Wednesday in the journal Nature, the researchers reanalyzed a cache of fossils and concluded that the earliest pterosaur relatives were off to a running start long before they took off.

The team examined several sandstone blocks that were excavated around the turn of the 20th century from a quarry in northern Scotland. Known as the Elgin reptiles after a nearby Scottish town, these dense hunks of rock entomb the remnants of armor-clad ancestral crocodiles, early dinosaurs and lizards from the late Triassic Period, or 237 million years ago. One of the smallest animals found in these rocks is Scleromochlus, a slender reptile that could fit in the palm of a hand.

Since its discovery in the early 1900s, Scleromochlus has perplexed paleontologists. Its fossils are difficult to study because the bones disappeared long ago, leaving behind empty spaces within the sandstone. For decades, researchers have poured latex or wax into these voids to create casts. But these methods often miss intricate traits.

0be96aaa-7e7d-4a6f-a72f-598748fc43d2.jpg
A 3-D skeletal reconstructions of Scleromochlus taylori

So instead of forging manual molds, Dr. Foffa, then at the National Museum of Scotland, and his colleagues placed several blocks containing Scleromochlus specimens under a micro CT scanner. This allowed them to digitally reconstruct the skeleton of Scleromochlus in three-dimensions.

Scleromochlus may look like a lanky dinosaur crossed with a chameleon. But after further examination, the researchers identified several traits that Scleromochlus shared with lagerpetids, a group of small reptiles that scurried around Pangea during the Triassic Period. That includes an oddly large skull for its size and a hooked femur head that slots into the hip vertically instead of splayed out to the side like a lizard’s leg.

According to Stephen Brusatte, a paleontologist at the University of Edinburgh and one of Dr. Foffa’s co-authors, lagerpetids appear to have been agile, bipedal creatures reminiscent of pint-size dinosaurs. Their anatomy, however, reveals a much closer affinity to pterosaurs. “At a quick glance, they look nothing like a pterosaur,” Dr. Brusatte said. “But a close look at their skeletons and the similarities with pterosaurs became apparent, like invisible ink being held to the light.”

If Scleromochlus is an early relative of pterosaurs, it challenges the assumption that pterosaurs initially jumped or glided. Scleromochlus lacked the sturdy hips of a hopping animal like a frog and would have been an awkward fit in trees, according to Kevin Padian, a paleontologist at the University of California, Berkeley, who has studied pterosaur evolution for decades. “They’re long-legged and short-armed,” said Dr. Padian, who was not involved with the new study. “That’s not how an arboreal animal like a squirrel is built.”

Instead, Scleromochlus was most likely more comfortable swiftly pursuing insects on the ground. This left its forearms free, potentially setting the stage for animals in its branch of the family tree to eventually flap. “Using their forelimbs for other functions could have been related to the evolution of new habits, including active flight in the case of pterosaurs,” said Martin Ezcurra, a paleontologist at the Argentine Museum of Natural Sciences who was not involved in the new study.

Dr. Foffa stresses that more fossil evidence is required to connect Scleromochlus with the earliest true pterosaurs. “It doesn’t have wings or anything crazy like that,” he said. “The crazy comes later.”


Source

© Copyright Original Source

The abstract from the paper Scleromochlus and the early evolution of Pterosauromorpha is available below, the entire paper MAY be accessible HERE ( smiley fingers crossed.gif)

Abstract

Pterosaurs, the first vertebrates to evolve powered flight, were key components of Mesozoic terrestrial ecosystems from their sudden appearance in the Late Triassic until their demise at the end of the Cretaceous^1,2,3,4,5,6. However, the origin and early evolution of pterosaurs are poorly understood owing to a substantial stratigraphic and morphological gap between these reptiles and their closest relatives⁶, Lagerpetidae⁷. Scleromochlus taylori, a tiny reptile from the early Late Triassic of Scotland discovered over a century ago, was hypothesized to be a key taxon closely related to pterosaurs⁸, but its poor preservation has limited previous studies and resulted in controversy over its phylogenetic position, with some even doubting its identification as an archosaur⁹. Here we use microcomputed tomographic scans to provide the first accurate whole-skeletal reconstruction and a revised diagnosis of Scleromochlus, revealing new anatomical details that conclusively identify it as a close pterosaur relative¹ within Pterosauromorpha (the lagerpetid + pterosaur clade). Scleromochlus is anatomically more similar to lagerpetids than to pterosaurs and retains numerous features that were probably present in very early diverging members of Avemetatarsalia (bird-line archosaurs). These results support the hypothesis that the first flying reptiles evolved from tiny, probably facultatively bipedal, cursorial ancestors

The imagifications

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Artist reconstruction

[Ronson]

scot.jpg

[rogue06]

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[*Refusing to take this as anything but serious*]

Interestingly haggis is not uniquely Scottish. It was a Gaelic dish known pretty much from Greece to the British Isles in long gone times. It's just that as better food came along it's only the Scots who not only cling to it, but darn near venerate the nasty thing.

[Ronson]

Oh, I couldn't even spell it right. And I am supposed to be 2% Scottish.

[rogue06]

Oh, I couldn't even spell it right. And I am supposed to be 2% Scottish.

No True Scotsman