Cratonavis zhuiA new species of pygostylian bird, ‘, was discovered in the Early Cretaceous Jehol biota of China. It had a rare combination of a dinosaurian skull and an avialan, post-cranial skeleton. This reveals the importance of evolutionary mosaicism for early bird diversification.
Cratonavis zhui Living in China, circa 120 million years ago during the Early Cretaceous period.
It is located between the members of bird clade on the bird evolutionary tree. Ornithothoraces The more reptile-like Archaeopteryx.
“The Cretaceous is an important time period that includes explosive diversifications of terrestrial vertebrates,” stated Dr. Min Wang and his colleagues. They are both researchers with the Institute of Vertebrate Paleontology and Paleoanthropology, and the Center for Excellence in Life and Paleoenvironment of the Chinese Academy of Sciences.
“This diversity in the early stages is overpowered by Ornithothoraces consisting of Enantiornithes, Ornithuromorpha and Ornithuromorpha whose members developed key derived characteristics of crown birds.”
This disparity explains why there is a significant morphological difference between the derived clades of oldest birds and these derived ones. Archaeopteryx.”
The research was conducted by Dr. Wang with co-authors. They examined the skull as well as the post-cranial structure. Cratonavis zhui Using the high-resolution computerized tomography.
The skull was morphologically almost identical to the one of dinosaurs, such as Tyrannosaurus rex.
The primitive features of the cranials indicate that Cretaceous birds like Cratonavis zhui Their upper bills could not be moved independently from their braincase and lower jaw. This functional innovation is widely shared among living birds and contributes greatly to their ecological diversity,” stated Dr. Zhiheng Li of the Institute of Vertebrate Paleontology and Paleoanthropology and also the Center for Excellence in Life and Paleoenvironment of the Chinese Academy of Sciences.
“The scapula Cratonavis zhui It is vitally important for avian flight and conveys stability, flexibility,” added Dr. Wang.
We traced changes in the scapula throughout the theropod/bird transition and suggested that an elongate capula might increase the mechanical advantage for muscle for humerus retract/rotation. These differences are morphological experiments in early bird diversification.
Our study found that the first metatarsal was selected during the transition from dinosaur to bird, which favors a shorter bone.
It then lost its evolutionary ability once it was at its ideal size of less than 25% of its second metatarsal.
Dr. Thomas Stidham also of the Institute of Vertebrate Paleontology and Paleoanthropology and of the Center for Excellence in Life and Paleoenvironment of the Chinese Academy of Sciences, stated that “but, increased evolutionary lability existed among Mesozoic birds and kins of dinosaurs, which could have been due to conflicting demands associated its direct use of the hallux in locomotion and food.”
“For Cratonavis zhuiThis elongate and long-lasting hallux is likely due to selection for raptorial behaviour.
“The preserved aberrant morphologies in the metatarsals and scapula” Cratonavis zhui Highlight the breadth of bone skeletal plasticity in birds early on,” stated Dr. Zhonghe Zhou from both the Institute of Vertebrate Paleontology and Paleoanthropology and also the Center for Excellence in Life and Paleoenvironment of the Chinese Academy of Sciences.
“Changes to these elements in the theropod trees show clade-specific evolution lability which results from interplay between development, natural selection and ecological opportunity.”
These findings were published by the journal Nature Ecology & Evolution.
Z. Li The authors and others. The skull and skeleton are separated in Cretaceous birds with distinctive appendicular shapes. Nat Ecol Evol, published online January 2, 2023; doi: 10.1038/s41559-022-01921-w