Small dinosaurs grew slower in harsh environments

Small dinosaurs grew slower in harsh environments

Not knowing much about noasaurs I found this paper rather interesting!  Released in September, 2020 and written by Souza et al., the team studied the bone growth (histology) of the small (4' long and 30 lbs.) Brazilian noasaurid theropod Vespersaurus paranaensisThe name means "Parana's West Lizard" (named after the town of Western Cross [English translation]) and it has one one of the coolest dinosaur feet ever discovered as one toe bore the majority, if not all, of the weight of the animal. 

Vespersaurus foot

This is Figure 10 D from its original description showing the long toe (link to paper here)

This differs from all other known meat-eating dinosaurs, who spread the weight across 3 toes.  Its toe claws had sharp bottoms (not sharp tips), suggesting they were used for scratching the ground and not kicking other animals offensively or defensively. 

Noasaurids aren't the most well-known of dinosaurs.  The best understood, Masiakasaurus, had a fascinating lower jaw that curved down strongly at the tip, making the lower teeth jut forward.  It likely used these teeth to eat fish and invertebrates.  Perhaps Vespersaurus used its sharp claws to dig up insects?

Small meat-eating dinosaurs typically grow very quickly based on numerous histology studies across numerous kinds of dinosaurs.  This study, however, concluded that Vespersaurus grew slow and steady, that it didn't go through a rapid growth stage when young like all other dinosaurs!  How slow did it grow?  Vespersaurus reached sexual maturity between 5 and 10 years old and, over that time, grew to a little over 4' in length.  Souza and his team of co-authors believe the reason these dinosaurs grew slowly was because they lived in a harsh climate, in this case an arid landscape with minimal food resources.  The only other small, slow-growing, meat-eating dinosaur?  The aforementioned Masiakasaurus, a small carnivore from Madagascar that lived in an equally hostile environment and is close cousin of Vespersaurus.  It is possible that growing slow will ultimately prove to be a character that can be used to identify future members of the Noasauridae.  Interestingly, noasaurs are related to abelisaurids, the ultra-short-armed carnivores of which Carnotaurus is the most famous.  The more dinosaurs we discover from around the world the more mysteries we find!



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