Episode 388: The largest megaraptorid ever?. Maip macrothorax was a huge megaraptorid and a not-too-distant relative of Tyrannosaurus. It also had an impressively bulky body to go with its presumably fearsome claws.

You can listen to our free podcast, with all our episodes, on Apple Podcasts at: https://itunes.apple.com/us/podcast/i-know-dino/id960976813?mt=2

News:

• A new massive megaraptorid, Maip macrothorax, was described from Patagonia source
• A new ornithomimosaur (not yet named) has been found in the Erlian Formation of Nei Mongol, north China source
• The University of Colorado Boulder is returning their Triceratops skull to the Smithsonian Institution source
• The game Parkasaurus is now available on Nintendo Switch source
• Colin Trevorrow shared a map of Jurassic World: Dominion that showed where the dinosaurs have ended up around the U.S. source
• Jurassic World: Dominion dropped a second trailer source
• Tom Holtz shared a flowchart to help determine if you’ve found a coprolite, regurgitalite, or other dinosaur meal source

Sponsors:

This episode is brought to you by our patrons. Their generous contributions make our podcast possible! You can join our community, help us keep the show going, and get the show ad-free for $9/month with an annual subscription. Go to Patreon.com/iknowdino to sign up.

The dinosaur of the day: Anchiornis

• Paravian dinosaur that lived in the Late Jurassic in what is now Liaoning, China (Tiaojishan Formation)
• Looks a lot like a bird, but with feathers on its legs, and teeth, and often depicted as having lots of feathers on its head (almost like a crest)
• In Jurassic World: Camp Cretaceous, Darius Bowman mentioned Anchiornis as a possible new dinosaur in Jurassic World, that was announced while he was visiting his father in a hospital
• Somewhat similar to modern birds
• Closest relative of Aves
• Anchiornis is about 5 to 10 million years older than Archaeopteryx
• Small, with four wings
• About the size of a crow or pigeon
• Originally estimated to be 13 in (34 cm) long
• Holotype estimated to be 34 cm long “reinforces the deduction that small size evolved early in the history of birds,” according to the original paper
• Some specimens larger, so could be up to 16 in (40 cm) long and weigh 0.55 lb (0.25 kg)
• Estimated to weigh about 0.24 lb (110 g)
• Bipedal, with a triangular skull
• Had small, unserrated teeth
• Had a slender, short scapula
• Had long arms, long legs, and a long, bony tail
• Forelimbs were about 80% the length of the hindlimbs
• Had an elongate hindlimb
• Had long legs, but may not have been a strong runner (runners tend not to have lots of hair or feathers on legs)
• Had four toes on each foot, and the third and fourth toes were the longest
• First toe (hallux) was not reversed, the way it is in animals that perch (probably didn’t perch)
• Skin and muscle tissue have been found
• Type and only species is Anchiornis huxleyi
• Described by Xu Xing and others in 2009
• Genus name means “near bird”
• Species name refers to Thomas Huxley, “who pioneered research into avian origins”
• Huxley was one of the first to suggest a connection between birds and dinosaurs
• Type specimen is articulated, missing the skull, part of the tail, and right forelimb
• Holotype includes articulated skeleton (no skull), cervical vertebrae, posterior caudal vertebrae, and “faint feather impressions preserved on the slab and counter slab”
• Holotype is probably a sub-adult or young adult “complete fusion of all the post-cervical vertebral neurocentral sutures”
• No LAGs
• Second specimen found was larger and more complete, with long wing feathers on the hands, arms, legs, and feet
• Hundreds of specimens have been found
• Shandong Tianyu Museum of Nature in Pingyi County, China, reportedly has 255 Anchiornis specimens in their collections, as of 2010
• Covered in feathers, with some scales
• Had long, narrow vaned feathers on the wings, legs, and tail
• Had two types of downy feathers on the rest of its body
• Had long feathers on the head that may have formed a crest
• Wing span up to 20 in (50 cm)
• Wing had 11 primary feathers and 10 secondary feathers, and formed a rounded wing
• Wing feathers were symmetrical, so not great for flying
• Longest wing feathers were near the wrist, so the wing was broadest in the middle and tapered near the tip (looked more rounded)
• Had a flap of skin that connected the wrist to the shoulder (propatagium), covered in feathers that covered the gaps between the primary and secondary feathers
• Feathers not arranged in tracts or rows (unlike modern birds)
• Had covert feathers that covered most of the wing’s surface
• Had long, vaned feathers on the hind legs
• Hindwings had 12 to 13 flight feathers on the lower leg and 10 to 11 on the upper foot
• Hindwing feathers were the longest closest to the body
• Made it look like a four-winged dinosaur (similar to Microraptor and Sapeornis)
• Feet, other than the claws, were covered in feathers
• Foot feathers were short and pointed downward
• A 2010 study looked at melanosomes in Anchiornis feathers and compared them to modern birds
• Figured out almost all of its color (except the tail, which was missing)
• First dinosaur where we knew its color was Sinosauropteryx (had a banded orange and white tail)
• Two main types of melanosomes: eumelanosomes (black-grey shades, tend to be long and sausage-shaped) and phaeomelanosomes (reddish to yellowish, tend to be rounder and jelly bean shaped)
• Help to figure out the colors in dinosaurs
• Study showed that Anchiornis had a feathered crest on the head
• Most of the body was gray and black, crown feathers were reddish-brown with a gray base, and the face had reddish-brown speckles among mostly black feathers. Wing feathers were white with black tips, and covert feathers were gray. Larger coverts on the wing were also white with gray or black tips, to form rows of darker dots on the mid-wing (looked like stripes of even rows of dots on the outer wing, and uneven speckles on the inner wing)
• Legs were mostly gray, and feet and toes were black
• A 2015 study of a different Anchiornis specimen found only gray-black melanosomes, without any reddish color in the crown
• Possible that melanosomes were preserved differently or there were different investigative techniques used, or the first specimen was smaller, and it could be the reddish-brown color got replaced as Anchiornis grew older. Or could be due to regional differences or they were different species of Anchiornis
• In 2010, Quanguo Li and others looked at the melanosomes of Anchiornis feathers, and suggested the feathers were for finding mates or other communication (defense postures, startling predators, sending warning signals)
• In 2015, Johan Lindgren and others looked at the molecular structure of feathers in an Anchiornis specimen, and found “unequivocally […] that melanosomes can be preserved in fossil feathers” (some debate before about them being indistinguishable from microbes in skin tissue that colonize during decay)
• In 2012, Nicholas Longrich and others analyzed wing feather arrangement in Archaeopteryx and Anchiornis, and found they had multiple rows of feathers
• Found that Enantiornithes had modern wings (oldest one, Protopteryx, from 131 million years ago, which is about 25 million years after Anchiornis, so may mean that the wing feather arrangement in modern birds evolved over tens of millions of years and then stayed mostly the same for more than 130 million years)
• Feather arrangement packed together layers of relatively weak feathers, which may have made them strong enough to work like airfoils (produces lift and drag when moved through the air), which would have been thicker than those in modern birds, increasing drag at low speeds and decreasing drag at higher speeds
• Overlapping feathers would make it difficult to take off from the ground
• In 2017, Evan Saitta and others found Anchiornis to have a “‘shaggy,’ open-vaned, bifurcated feather with long [flexible] barbs attached to a short rachis”, probably used for thermoregulation and repelling water, and combined with open-vaned wing feathers “would have decreased aerodynamic efficiency”
• Looked fluffy
• In 2019, Yanhong Pan and others, analyzed Anchiornis feathers and found alpha-keratins (usually only found in modern feathers) and beta-keratins, modified in a way that makes the feathers more flexible
• Analyzed feathers from Anchiornis and compared to other fossil feathers and modern flight feathers (from a chicken, goose, duck, emu)
• Found modern birds had mostly beta keratins in mature feathers, whereas Anchiornis had beta-keratins and alpha-keratins in its feathers
• Further showed that feathers may have at first evolved for reasons other than flight
• Means that this modification happened earlier than previously thought. Flight feathers were thought to evolve about 145 million years ago, and lived about 160 million years ago, so Anchiornis feathers helps show how feathers evolved for flight
• Originally thought Anchiornis could fly or glide, but later found the wings were too short
• A 2016 study found juvenile Anchiornis may have been able to use wings to help run up hills, and maybe could fly while flapping if using a high angle flapping wing stroke, but adults would have been too heavy to fly
• Flapping while running would have sped it up about 10%
• Flapping while leaping would increase the height and distance by around 15% to 20%
• In 2009, Xu Xing and others described Anchiornis, and wrote “some wrist features indicative of high mobility, presaging the wing-folding mechanisms seen in more derived birds and suggesting rapid evolution of the carpus”
• Also said Anchiornis “represents a transitional step toward the avian condition”
• Had a more avian-like wrist than other non-avian theropods
• Avian wrist is modified for wing folding and flying
• Xiaoting Zheng and others in 2014 analyzed 226 Anchiornis specimens and 96 Sapeornis specimens and found no sternum in either
• May have no sternum, which “could represent the plesiomorphic avian condition”
• Ossified sternum sometimes missing in fossil birds. Not having a sternum “suggest that flight capabilities would be severely limited in basal birds”
• Found in Anchiornis and Sapeornis, the absence of sternal elements are “a true feature of these taxa and not an artifact of preservation or ontogeny”
• Used histology, found all the specimens to be mature
• Possible the gastralia may have supported the muscles needed for gliding (if it glided), but it’s unclear
• A 2010 study by Alexander and others found Anchiornis to be a glider
• In 2014 Garnet Fraiser suggested the long legs of Anchiornis could be related to “dorsal riding parasitic behavior” (riding on the backs of other animals), and used for “running, jumping and climbing over plates and spikes. The need for a gliding dismount would explain long feathers on those long legs”
• Had large claws on the third digit of its feet, in addition to the sickle-shaped second claws
• Foot pads covered in small, pebble-like scales
• Had scales on the top of the feet
• Some Anchiornis had scales on the toes, tarsus, and lower leg, so maybe had scales beneath the feathers
• Had three clawed fingers, where the longest two fingers were stuck together with skin and tissue from the wing (so basically only had two fingers)
• Skin around the bottom of the fingers and the toes were covered in tiny, rounded scales
• In 2018, Xiaoting Zheng and others studied six gastric pellets attributed to Anchiornis, which had “lightly acid-etched lizard bones or fish scales”
• Made Anchiornis the earliest, most basal known theropod known to produce gastric pellets
• Only definitively known gastric pellets from any non-avialan theropod
• Pellets were similar to those of modern birds
• Pellets are undigested parts food that are regurgitated
• Helps show a digestive system similar to modern birds, “and that the evolution of modern avian digestion may have been related to the appearance of aerial locomotion in this lineage” (birds have a high metabolism)
• Anchiornis had a two-chambered stomach, efficient antiperistalsis (propels food from the stomach back up to the mouth), low stomach acidity, and short gastric residence, which may mean this specialized digestive system, also seen in birds, was ancestral in Paraves or even Maniraptora
• Regurgitating would have improved Paraves’ digestion efficiency, which may have helped give it energy for aerial locomotion, and early paravians could also have quickly gotten rid of any non-digested food, to make themselves lighter quickly
• Anchiornis was probably an opportunistic generalist hunter
• Presence of three lizard skeletons found in one pellet
• Fish may have been a big part of its diet, based on five of the six pellets containing only fish scales
• Anchiornis didn’t seem great for catching fish. Compared to birds that live near water, it had lots of feathers below the knee, and it had a relatively short snout (usually birds that catch fish have long, slender bills)
• Fish found could mean Anchiornis could catch some fish, or there’s a preservation bias for the fish-bearing pellets and it doesn’t show its true diet
• Lived in a subtropical to temperate climate, that was warm and humid
• Other dinosaurs that lived around the same time and place include other bird-like dinosaurs Aurornis, Eosinopteryx, Scansoriopteryx, Serikornis, and Xiaotingia, and the heterodontosaur Tianyulong
• Other animals that lived around the same time and place included pterosaurs, salamanders, insects, arachnids, and mammals

Fun Fact:

Aside from Anchiornis, few fossilized gastric pellets have been found with non-avian dinosaurs.

Thank you Patrons!

Your support means so much to us and keeps us going! If you’re a dinosaur enthusiast, join our growing community on Patreon at patreon.com/iknowdino