Friday, 7 February 2014

My old online article from BDW (1999)

Triceratops by BeriMimi

Mesozoic Mosaic pg #2

Illustration of Sinornithosaurus - by Beri (digital), Copyright © 1999-2004 BERI
Commissioned and first published in online by:

Sep 1999

Sinornithosaurus - a feathery dromaeosaurid
Sinornithosaurus millenii Xu, Wang & Wu, 1999

References: (dead link)
HWANG, S.H., M.A. NORELL, JI Q., and GAO K. 2002. New Specimens of Microraptor zhaoianus (Theropoda: Dromaeosauridae) from Northeastern China. American Museum Novitates 3381: 1–44.
Sinornithosaurus millenii, XING XU, XIAO-LIN WANG & XIAO-CHUN WU, 1999  

Holotype. IVPP (Institute of Vertebrate Paleontology and Paleoanthropology) V12811 .   

Locality and horizon. Sihetun, western Liaoning, China. Layer 6, lower (Chaomidianzi) Yixian Formation, Jehol Group; probably Early Cretaceous.   

 Didn't paleoartists (led by McLoughlyn, Baker and Paul) predicted it would be discovered that dromaeosaurs were covered with some sort of hairy proto-feathers, a deduction based upon the close anatomical resemblance of dromaeosaurs and birds? 

Well, the long awaited hard evidence was finally presented in today's issue of Nature magazine (16 Sept.,1999). Spielberg's "Jurassic Park" naked, scaly "raptors" (even this term was scientifically wrong - because it refers to the extant bird of prey genus) are doomed to be tossed in the rich archives of dinosaur misinterpretations. There is little doubt now that Deinonychus, depicted in a Hollywood manner in the movie, was too "dressed" in the feathers.  

Although considered to be well known by everybody, especially after dinosaur movie planetary success, dromaeosauridae were known only form a few mainly incomplete fossils (the exceptions were some fine Mongolian specimens), so a lot of things about them were not entirely clear. Chinese paleontologists have recently found and described a fine dromaeosaurid fossil in Yixian Formation of China (Locality and horizon. Sihetun, western Liaoning, China. Layer 6, lower (Chaomidianzi) Yixian Formation, Jehol Group; probably Early Cretaceous - dated to about 125 million years ago), with a filamentous integument (a downy coat). The new feathered sensation from China was coined Sinornithosaurus millenii. The genus name is derived from Sino + Ornitho + Saurus, for " a bird-like dinosaur from China;" while the species name comes from "Millennium," in reference to the specimen's discovery near the end of the twentieth century.  

The animal was rather small even for a dromaeosaurid. Its skull was about 13 cm (5,1") long, which gives the derived, approximate total length (the tail in dromaeosaurs was very long) of this dinosaur of about 110cm (43,3"). The "downy coat" was made up of filaments which were up to 4 cm (1.6") long, those filamentous structures near the cranium (skull) seem to be shorter than the postcranial fibers.  Further preparation of the specimen could reveal more fibers.  The insulation looks more like the fur than the modern birds' feathers, which look kind of furry in the picture (not like well-structured wing feathers)." The skeleton is not well articulated, but the bones are a bit jumbled and the integumentary filaments have been displaced, lacking the direct relationships to bony elements." But they are certainly close enough to enable rough determination. The skull, arms, legs, scapulae, coracoids, sacrum, a manus, a pes, and the furcula are all quite reasonably represented by the holotype, however, many vertebrae and rib elements are missing.  

"Sinornithosaurus millenii gen. et sp. nov. comes from Sihetun, the famous Mesozoic fish-dinosaur-bird locality in China.. It is the oldest known dromeosaur (a basal dromaeosaurid) and its fossil "strongly supports the view that Dromaeosauridae and birds (where Aves is Avialae) are more closely related to each other than either is to Troodontidae ." Authors of the article state their analysis also indicates that Protarchaeopteryx and Caudipteryx are more remote from birds than is Troodontidae. "The currently established phylogenetic relationships among derived theropods seem to support the presence of true feathers in Dromaeosauridae, but the validity of this interpretation cannot be confirmed until more direct evidence is available."  

"Sinornithosaurus not only greatly increases our knowledge of Dromaeosauridae but also provides evidence for a filamentous integument in this group. It is remarkably similar to early birds postcranially" (skeleton behind the skull). "The shoulder girdle shows that terrestrial dromaeosaurids had attained the prerequisites for powered, flapping flight, supporting the idea that bird flight originated from the ground up. The discovery of Sinornithosaurus widens the distribution of integumentary filaments among non-avian theropods."  

The authors of the article XING XU, XIAO-LIN WANG & XIAO-CHUN WU claimS. millenii could apparently flap its long front limbs in a bird's mode. The evidence supposedly lies in the structure of the animal's shoulder girdle. That is, the lateral position of the glenoid (shoulder socket) would have permitted elevation, rotation and adduction of the forelimbs, providing Sinornithosaurus a wide range of arm movement similar to the capabilities of the fabled early bird Archaeopteryx.  The forelimbs were unusually long (claws well preserved, even with a horny sheath - keratin; long and curved), estimated to be 80% as long as the dromaeosaur's legs. The paired, ossified sterna possess a series of (probably five) costal facets (rib attachments), implying hinged sternocostal joints.  

Sinornithosaurus is the fifth kind of theropod known to possess integumentary filaments. It is possible that these filaments indicate an insulatory layer that served to maintain body heat.   

Authors suggest that the fossil provides more "evidence that the first birds took off from the ground, evolving from fast-running two-legged predatory dinosaurs called theropods". Is this almost the final answer to the famous dilemma: Did the bird's flight evolve from the ground up or from the trees down?  

Well, I suggest a new solution to the problem: knowing that we've got very intelligent birds today, say African Gray parrot (Psittacus erithacus) could learn the kinds of symbolic and conceptual tasks that are generally considered as pre- or co-requisites for complex cognitive and communicative skills, why don't we ask such a smart feathery critter (who can fly), what is easier to him: To fly up from the ground or down from a branch? I am sure we'll get the straight answer.  


Reference: XING XU, XIAO-LIN WANG & XIAO-CHUN WU - A dromaeosaurid dinosaur with a filamentous integument from the Yixian Formation of China , Nature 401, 262 - 266 , September 16 1999 (1999) © Macmillan Publishers Ltd.   

The Nature paper discusses the specimen in considerable detail:  

on-line: NATURE  

Published in 1999 in now extinct online magazine: DIM Extra 4/1 (VOL 2)     

Publishers interested in the above illustration (high resolution image for publishing purposes), please, contact Beri.

UPDATE (Feb.2014)

In the paper published 10 years later, authors claim this dromaeosaur from China's Jehol formation had grooved fangs as a venomous delivery system. In other words, Sinraptor's killing technique was something between a venomous snake and a Heloderma lizard.

The birdlike raptor Sinornithosaurus was venomous

 Enpu Gonga, Larry D. Martinb, David A. Burnhamb and Amanda R. Falkc
Reference: PNAS doi:10.1073/pnas.0912360107
 Edited by David B. Wake, University of California, Berkeley, Berkeley, CA, and approved November 16, 2009 (received for review October 26, 2009) 


We suggest that some of the most avian dromaeosaurs, such as Sinornithosaurus, were venomous, and propose an ecological model for that taxon based on its unusual dentition and other cranial features including grooved teeth, a possible pocket for venom glands, and a groove leading from that pocket to the exposed bases of the teeth. These features are all analogous to the venomous morphology of lizards. Sinornithosaurus and related dromaeosaurs probably fed on the abundant birds of the Jehol forests during the Early Cretaceous in northeastern China.


No comments:

Post a Comment