I Know Dino Podcast Show Notes: Sinornithosaurus (Episode 244)

Episode 244 is all about Sinornithosaurus, an early raptor from China that was covered in feathers.

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In this episode, we discuss:

News:

A new census of the Lance & Hell Creek Formations found at least 71 T. rex skulls & skeletons source (pdf)
A database of over 3,000 sauropod specimens from the Morrison Formation has been published source
Broken ribs, toes, and a bone infection were found in an unfortunate Tenontosaurus source

A helitack crew in Colorado picked up “Walter” in two plaster jackets that weighed over 1,000 pounds each source
A new dinosaur museum opened up in Wolcott, Colorado source
On September 15, animatronic dinosaurs are going to be at the Bath Racecourse in the UK source

Springs Preserve in Las Vegas has a new exhibit called Dino Might source
The Science Museum of Minnesota recently finished their first Dino Fest source
Two Chinese paleontologists have made a complete rendering of the bipedal Auroraceratops source

The dinosaur of the day: Sinornithosaurus

Dromaeosaurid that lived in the Early Cretaceous in what is now Liaoning, China (Yixian Formation)
Basal dromaeosaur

Helps show that earlier dromaeosaurs were more like birds than later dromaeosaurs
Small, about 3 ft (1 m) long, though Gregory Paul estimated it to be 3.9 ft (1.2 m) long and weigh 6.6 lb (3 kg)
Had feathers, similar to Archaeopteryx

Preserved impressions of feathers found on the whole body and forming the wings (feathers looked the same as feathers found on birds from the same area)
Had two types of feathers, one type like modern down feathers and one time like modern bird feathers, though they looked a little different from flight feathers (no continuous vane)
Had different colored feathers around its body. A 2012 study found they were reddish-brown, yellow, black, and grey

May have been able to glide short distances after jumping from trees
In 2018 McNamara and others analyzed the fossilized skin of Beipiaosaurus, Sinornithosaurus, Microraptor, and Confuciusornis. They used electron microscopes to study their fossilized dandruff
Helps show how dinosaurs shed their skin

They found it to be nearly the same as to dandruff in modern birds
Sinornithosaurus shed skin in flakes, like modern birds and mammals (didn’t shed at once like a lizard or other reptiles)
Found that feathered skin had evolved many (not all) modern attributes by the time maniraptorans came about in the Middle Jurassic

Shows evidence that early birds and dinosaurs were evolving skin in response to having feathers (the fossilized dandruff is made of corneocyte cells, which when alive are dry and full of keratin (modern birds have fatty corneocytes with loosely packed keratin to help them cool down quickly when flying for long periods of time)
The fossilized skin had packed keratin which may mean the dinosaurs didn’t get as warm as modern birds, possibly because they either couldn’t fly or couldn’t fly for long periods of time
Carnivorous, probably ate small animals

Had a sickle-shaped toe claw
May have been cathemeral (active throughout the day and night in short spurts)
Described in 1999 by Xu Xing and others (found an almost complete fossil with feather impressions)

Type species is Sinornithosaurus millenii (name means “millennium Chinese bird lizard”)
Second species is Sinornithosaurus haoiana (“Hao’s Chinese bird lizard”), described in 2004 by Liu and others based on a second specimen found that had different skull and hip features
However, Turner, Makovicky, and Norell in 2012 suggested that Sinornithosaurus haoiana was a junior synonym of Sinornithosaurus millenii

Another specimen, nicknamed “Dave” was described in 2001 but not named. Ji and others formally referred “Dave” to Sinornithosaurus in 2002 but said it may be questionable. Stephen Czerkas and others said they thought “Dave” was a specimen of Cryptovolans pauli (now considered to be Microraptor gui). Then in 2011 Senter said the holotype of Sinornithosaurus was similar to “Dave” and that “Dave” was a Sinornithosaurus millenii
A 2012 paper by Turner, Makovicky, and Norell agreed, and found “Dave” to be a subadult Sinornithosaurus millenii
Holotype is at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China

In 2009, Empu Gong and others suggested that Sinornithosaurus was venomous, based on its skull. They found it had long and fang-like maxillary teeth with prominent grooves (long teeth, as seen in venomous animals such as snakes, and the grooves provided a channel for the venom, and they said the cavity in the jaw bone above these teeth may have been for a venom gland. Because of this, they also suggested Sinornithosaurus hunted small prey, such as birds, and used its fangs to stun the prey (bite and hold)
Thought it had a low bite force and used fangs to puncture through feathers, inject venom, and shock its prey. Also the teeth at the front of the snout angled forward, which may have been used to pluck feathers
In 2010, Federico Gianechini and others suggested that Sinornithosaurus was not venomous, because the grooved teeth are not unique to Sinornithosaurus (seen in other theropods, including other dromaeosaurids), and that the teeth were not as long as Gong and others thought they were, but that they had come out of their sockets so they seemed longer. Also, they couldn’t find the cavity that supposedly held the venom gland. They only found normal sinus cavities

At the same time, Gong and his team published a reassessment of Gianechini and his team’s study. They said that though grooved teeth are common in theropods (mostly feathered maniraptorans), they hyopthesized venom was possibly a primitive trait for all archosaurs and stayed in some lineages. They also did not think the teeth were out of their sockets, though they said they were not totally in their natural position (they said some undescribed specimens had full articulated teeth that were similarly long)
Consensus seems to be that there is no clear evidence that it was venomous (need more detailed evidence)

Fun Fact: Deposits of the Latest Cretaceous (AKA Maastrichtian) go by many names—for good reason.

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