New Triassic fossil features sharp claws and a nasty beak

 

It was relatively small in comparison to the giants that would follow it later in Earth’s history. With a hip height of approximately 0.3 meters (about a foot) and a length of perhaps a meter (roughly three feet), this ancient reptile existed long before the evolution of the pterosaurs most of us recognize.

 

Its most striking features are its skull and hands, two body parts that rarely survive fossilization among similar animals this old. The skull consists of a raptorial-like beak without teeth, while its forelimbs end in long fingers with scimitar-like claws. These two surprising features are among many revelations in a paper published Wednesday in Nature.

 

Venetoraptor gassenae is the name of this new species of lagerpetid, a type of pterosaur precursor that lived about 230 million years ago in Brazil. Named for the district of Vale Vêneto in the same municipality in which the fossil was found—and for the plundering it might have done with its beak and claws ("raptor" is Latin for "plunderer")—it is also named to honor Valserina Maria Bulegon Gassen. Although not a paleontologist herself, the authors note that she is “one of the main people responsible for the CAPPA/UFSM” (the Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Universidade Federal de Santa Maria), a paleontological research support center).

 

This discovery augments an ever-growing number of dinosaur and pterosaur predecessor fossils coming out of South America. These rare finds, even with their fragmentary skulls and hands, unveil more about evolution and life during the early Triassic. But the partially articulated, well-preserved Venetoraptor is unique among such fossils; unearthing it was, according to lead author and discoverer Rodrigo Temp Müller, “one of the most exciting points of my career.”

Inspiring fear

Müller is a paleontologist at CAPPA/UFSM. He describes lagerpetids as “lightly-built animals that lived side-by-side with the first dinosaurs.” Although a fraction of the size of theropods like T.rex would evolve about 150 million years later, “their beak and claws surely [inspired] some fear to small animals” that co-existed with them.

 

It is exactly those two features that set Venetoraptor apart from other dinosaur and pterosaur precursors, as they provide evidence that these predecessors were a lot more morphologically diverse than previously understood. The beak appears to be without teeth, although they may not have been preserved. The team suggests it could have used it to eat hard fruit or tear flesh from prey. In extant birds, beaks also help with vocalization, thermoregulation, and sexual display.

 

Venetoraptor’s long hands may have helped it grab prey or even climb trees. And they indicate that the creatures walked bipedally. Not having to walk on all fours is, as interpreted by the team in the paper, “one of the main forces that drove the evolution of forelimb diversity within Ornithodira during the Late Triassic.”

 

Until 2020, it was thought that lagerpetids were closely related to dinosaurs. Evidence developed since suggests they are more closely related to pterosaurs, even if they couldn’t fly. This paper adds further evidence to support this thinking.

 

Müller noted that “at some point in evolutionary history, a common ancestor between lagerpetids and pterosaurs evolved advantages that led one of these lineages to dominate the skies.”

Crunching numbers on evolution

Co-author Martín Ezcurra is a paleontologist at the Sección Paleontología de Vertebrados, CONICET−Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” in Argentina. He was also the lead author on the 2020 paper providing evidence that lagerpetids are more closely related to pterosaurs. Since 2012, he’s been steadily working on a fossil data set, one he hopes to finish in 15 years.

 

“The idea,” he told Ars, “is to have a complete data set for all these reptiles that lived between 265 million years ago to 175 million years ago, which is a very important moment [in] reptile evolution.”

 

When the initial version of this data set was published in 2016, the year after he earned his PhD, there were 81 fossils represented. In the years since, that number has almost tripled. The team used this data set to perform a number of analyses to determine where Venetoraptor fit in the evolutionary tree and how it compared to other dinosaur/pterosaur precursors.

 

Ezcurra explained that numbers are assigned to every significant aspect of each bone, such as its shape and overall morphology. “With those numbers,” he said, “we build a matrix,” essentially encoding the anatomical structure of each animal. Having these numbers makes it easier to compare new finds to known species. Currently, there are 240 species in the data set, with 900 characteristics represented by numbers.

 

“So it’s a huge data set,” he continued. “It’s more than 200,000 different observations all transformed into numbers.” And with this, the researchers could build an evolutionary tree. Even on a powerful cluster and using parallelized code, the analysis still takes hours to days.

 

Beyond building evolutionary trees, the data set also allowed researchers to track the origin and migration of species and their descendants. Ezcurra said that three pieces of information were necessary to do this: knowing where each species fits on the evolutionary tree, the geographic location of the species as indicated by fossil discoveries, and its place in geologic time.

 

Equipped with these three things, the researchers determined that lagerpetids probably originated in South America. The team also found that some later members of the lagerpetid family discovered in North America were closely related to earlier South American lagerpetids. This indicates that at some point following their origin, the lagerpetids migrated north.

 

Using yet further computer analyses designed by the researchers, the team was able “to quantify the time and how many latitudinal degrees in the globe that [dinosaurs and lagerpetids] moved at the time.” They pinpointed that dispersal to shortly after a period termed the Carnian Pluvial Event, roughly 235 million years ago, a time of high global humidity and more abundant rains.

 

Separating the north and south portions of Pangea’s single landmass was an enormous desert. With the end of the Carnian Pluvial Event, the climate—specifically within the desert—was less extreme, enabling animals to cross it into the northern sections of the world.

 

Ezcurra’s data set also enabled the team to compare the morphologies of the dinosaur and lagerpetid species to each other, which created another matrix (the “dissimilarity matrix”), which generated “a ‘morphospace’ that plots all the species in a single area” and graphs how different they were from each other. “With that plot,” Ezcurra explained, “we saw that the diversity of these dinosaurs and pterosaur precursors was actually huge. Actually bigger than that of the first dinosaurs and similar to that of the first pterosaurs. So we concluded that dinosaurs and pterosaurs originated from a pool of diversity that was considerably bigger than previously thought.”

Revisiting the Triassic

Robin Whatley is a vertebrate paleontologist and associate professor at Columbia College Chicago who was not involved in the research.

 

“This is a great example of a study by a group of paleontologists who are working from their collective knowledge to describe various aspects of a new fossil with surprising features for an animal of its age,” she told Ars. “These authors highlight the unique combination of a tall, raptor-like beak and sharp claws with extended areas for the insertion of tendons that would allow grasping abilities, features that might give Venetoraptor increased abilities for climbing or manipulating food items. While it’s not possible to know exactly how Venetoraptor was using its beak and claws, these authors find compelling evidence for ecological diversity in this early ornithodire, well before diverse beak and limb morphologies show up in closely related dinosaurs and pterosaurs.”

 

The find also reinforces the critical role of South American fossils in our developing understanding of this time. “Over the past two decades, about 30 new species have been described from Triassic beds of Brazil, including forerunners to mammals and representatives of distinct lineages of archosaurs,” Marina B. Soares, co-author and associate professor at the Federal University of Rio de Janeiro, Brazil said in a press release. “In this regard, Venetoraptor gassenae stands out as a key fossil in understanding the morphological and ecological diversity seen in the precursors of the highly successful dinosaurs and pterosaurs.”

 

Nature, 2023.  DOI: 10.1038/s41586-023-06359-z