An exploration of our Earth's ever-captivating fauna through musings on the bizarre side of Zoology, Cryptozoology, Paleontology, and Paleoanthropology

Wednesday, December 26, 2012

A Review of 'All Yesterdays', A "New Look" For Dinosaurs That I Hope Stays!

 
I have had the pleasure to receive a fantastic book this Christmas, named All Yesterdays: Unique and Speculative Views of Dinosaurs and Other Prehistoric Animals. This book features amazing artwork and excellent novel ideas by John Conway, C.M. Kosemen, and Dr. Darren Naish. With the danger of revealing too much of what is in this wonderful new book, here is a bit of a review.
The cover of All Yesterdays with its beautifully illustrated, tree-climbing ceratopsians
 
What I love about this book is that it combines beautiful "paleoart" with bizarre, yet totally possible ideas about the appearance and lifestyle of dinosaurs and other prehistoric animals (such as plesiosaurs and a giant, pterosaur-eating centipede). The authors reconstruct dinosaurs with seemingly odd behaviors, yet fully support these hypothetical portrayals with evidence from the modern natural world. They do the same with the appearance and integument of some of their dinosaurs, and point out that modern animals aren't always sleek and often have body parts hidden by layers of fatty skin or integument. Accompanying text helps us understand why the authors reconstructed the dinosaur (or other prehistoric animal) on that page in the way they did, and a skeletal drawing is also present.
As a warm-blooded predator, a Tyrannosaurus would actually spend a large amount of time sleeping while digesting a meal.


A Majungasaurus with a stunning display, spreading its arms out "in a manner completely unlike that of other large predatory dinosaurs".
 
One of my favorite aspects of the paleoart in this book is that the authors put plenty of interesting integument on their dinosaurs. These included Therizinosaurus that have massive bodies hidden by feathers, Triceratops with large spike-like bristles, and Heterodontosaurus which are covered in bristly "hairs" and porcupine-like quills! Interestingly, we are learning that such speculation is quite plausible. Not only does fossil evidence support the idea of theropods with body integument such as feathers, but we are now learning that many small ornithiscians had fuzzy bristles as well.  
The authors of 'All Yesterdays' don't reconstruct their Leaellynasaura as naked, lizard-like animals.....
But rather, they reconstruct Leaellynasaura as being perfectly adapted to life in a polar climate with a fluffy integument. Brilliant!
Therizinosaurus are portrayed in this book as elephant-sized mounds of feathers with gigantic claws.
To help enforce their claim that it is perfectly reasonable to reconstruct dinosaurs with bizarre behaviors or anatomy, the authors also dedicated a chapter to reconstructing modern animals as a future paleontologist might if they only had fossilized remains to go off of. Some of the results were a terrifying hairless spider monkey, a cow with skin so tight that its bones show, and birds with membranes instead of feathers on their wings. This chapter truly impacted my way of thinking, and surely justified the paleoart styles of these artists. It also supports the idea that many dinosaurs may have been much thicker-bodied with muscle, fat, and/or bountiful integument. This book has the ability to thrill the minds of readers, and to make them realize that dinosaurs were probably a lot more bizarre-looking and acting than we often see them depicted as! However, it also shows that dinosaurs weren't strange and alien monsters, but were regular animals which probably behaved and looked like many species of the modern day.
A reconstruction of a modern cat that is "shrink-wrapped" and represents how modern paleontologists often wrongly depict dinosaurs as very slim, with every bone feature visible through the skin.
All Yesterdays is a truly amazing book, which I would fervently recommend to anyone interested in the possible appearance and lifestyles of dinosaurs. The art contained in the book is not only beautiful, but rejuvenating for the animals depicted. Hopefully, All Yesterdays will help end the era of depicting unrealistically leathery-skinned and slim dinosaurs and will bring forth reconstructions of the reptiles with the fuzzy integument and fatty skin that real animals have. In my mind, All Yesterdays depicts dinosaurs more accurately than other resources which I have seen in that it recognizes the bizarre habits and appearances that many modern animals have and brings them to life in dinosaurs. If only Jurassic Park had depicted its Triceratops with huge protective spines, although the famed Tyrannosaurus rex would be boring as it would be sleeping throughout the movie after consuming the goat and lawyer.
A spiny Triceratops from All Yesterdays. A  specimen of this ceratopsian at the Houston Museum of Natural Science has preserved skin impressions which suggest that these animals actually did possess such bristles. 

 I seriously can't say enough about All Yesterdays, and I emphatically hope that you buy it and read this fabulous book. If you have an open mind and even a slim interest in dinosaurs, this book will change your mind about the way they looked and acted for the better.

Friday, December 14, 2012

Hair, Bristles, and other Bizarre Anatomical Features in Ancient Reptiles

When you think of reptiles, you usually think of scaly animals. However, the truth is that many species of reptiles were likely far more bizarre. In this article, we will be exploring bizarre anatomical features of species of prehistoric reptiles; some features strange but real and some theoretical.

"Reptiles" (not really) with hair, warm blood, and milk glands

My very favorite drawing depicting two reptiles with a bizarre anatomical feature: fur!
Approximately 300 million years ago (Early Permian period), a group of truly bizarre reptiles existed called Therapsids. Believed to have evolved from reptiles called pelycosaurs, the earliest known therapsid was Tetraceratops.

Tetraceratops, likely the first therapsid species.
The therapsids are seperated into four major clades: the dinocephalians, the herbivorous anomodonts, the carnivorous biarmosuchians, and the mostly carnivorous theriodonts. The therapsids were unique reptiles in having an erect and mammal like posture made clear by the fact that therapsid feet were more symmetrical, with the first and last toes short and the middle toes longer.
The apparently rhinoceros sized therapsid, Inostrancevia, shown with its mammal like posture

Some species also had mammal like canines and molar teeth, a covering of hair, possibly warm blood, and possibly mammary glands!

Hair, and warm blood, and mammary glands, oh my!
A Dicynodont looking alot like a pig feeding its young. LOVE IT!
Now you know why the Therapsids are first on my article about bizarre ancient reptiles! As you probably guessed, the features mentioned above are what has caused scientists to theorize that the Therapsids were the ancestors of mammals. In fact, many scientists argue that therapsids are actually a seperate clade than reptiles and should be referred to as "stem-mammals". This classification makes my inclusion of them into an article about Ancient Reptiles inaccurate, but I am going to refer to them as stem-mammals from now on to justify the article.

I seriously can't get enough of Therapsid art!! A large, hairy Dicynodont!

What is truly bizarre and amazing about the therapsids (that lived a few million years after the cold blooded synapsids like Dimetrodon and Edaphosaurus) is that they were really proto-mammals!  They had a warm-blooded bone microstructure, a more mammal-like than reptile-like posture, and evidence exists that some had hair. This quote, from http://askwhy.co.uk/dinosauroids/?p=101, shows truly how mammal-like the therapsids were:
"Analysis of their fossils confirms that these also were warm-blooded. The external physiology (bumps for muscle attachment like the knee crest) and the internal physiology (bone texture) of therapsid bones point to warm-blood. Walking speeds calculated from fossil footprints were in the warm-blooded range and finally some of the therapsids lived at extreme latitudes where it must have been cool if not cold, making it probable that they had already evolved hair and were looking quite mammal-like. Rapid cycles of extinctions and repopulation tell us that these animals were warm-blooded—through active competition prone to mass extinction but able to restock the environment with new species by explosive adaptive radiation."
The Warm Blooded Therapsids, ancestors of the dominant species of today: mammals. (the turtle like reptiles are Scutosaurus, and are not therapsids but actually possible close relatives to the ancestor of turtles)
Now, I don't know how interesting that quote was to you but it makes a zoology nerd like very intrigued. Going back to the possibility of hair, there is some evidence that suggests that a few of these stem-mammals may have had hair. Skull features of therapsids such as Thrinaxodon (a cynodont that lived in Antarctica, although it was certainly not as cold as today) and some Gorgonopsids (the top predators of their time, some with sabre-teeth) suggest that they had whiskers. A very hilarious quote regarding gorgonopsians, from http://thedragonstales.blogspot.com, is this:
"Almost as though some poor pit bull woke up from a night that had one too many drinks to find it had done something wild and crazy with a Komodo Dragon. Then she had to live with the consequences of it."
A rather bizarre looking fossil skeleton of Thrinaxodon
A Gorgonospid
However, it seems that there is a problem for the idea of hairy therapsids that is so dear to my heart. Even more heart breaking is that the problem deals with my favorite therapsid, and makes it less bizarre. The problem for the hairy therapsid theory is a skin impression, which is still interesting as it shows great data regarding a therapsid species known as Estemmenosuchus.
The skull of arguably the coolest therapsid of them all: Estemmenosuchus 


Estemmenosuchus, arguably the most interesting and bizarre therapsid in my opinion (and I can argue for that statement), was a large and likely omnivourous stem-mammal that lived in the Middle Permian about 267 million years ago. They had bulky bodies and barrel-like chests and, due to being known primarily from channel flood deposits, is thought by some to have lived a semi-aquatic life. The skulls of Estemmenosuchus are totally bizarre, with massive bony and horned protuberances from the cheeks and upper skull. Not only were the cheek bones flared out to the side, this stem-mammal also had bony bumps that looked alot like the antlers of a moose!

Personally, I was hoping that this already bizarre therapsid would be very hairy and almost like a bulky moose with the body of a reptile and jaws of a hippo. Although moose don't have bizarre extending cheek bones or snout horns, their antlers are similar to Estemmenosuchus horns and the two relatives had similar snouts. My moose analogy is probably garbage, but it has been suggested that Estemmenosuchus had a similar lifestyle of occasionally being semi aquatic. Perhaps a reptilian "moose-hippo" would be better. Yes, that sounds good.

An Estemmenosuchus like modern mammal? Just add a reptile like body, hippo like jaws, extending cheek bones and a snout "horn", and also subtract hooves. Yeah, my moose analogy is garbage.
An Estemmenosuchid foraging in the water, just like a reptilian hippo-moose.
Going back to the previously mentioned Estemmenosuchus skin impression, the impression showed no sign of scales or hair (sadly). Instead it was said to have been a naked, mammal-like epidermis with many pores and glands. Some have suggested that the skin was probably similar to the skin of a rhinoceros.

A Square-Lipped Rhinoceros (White Rhinoceros) with skin possibly similar to an Estemmenosuchus
So sadly, the current evidence points to Estemmenosuchus not having hair. This may or may not apply to other therapsids. There is a good amount of evidence suggesting that some therapsids were warm blooded and it is known that some had whiskers. While it is very likely that late therapsids like cynodonts had hair, it is unknown if others did. Although we know Estemmenosuchus did not have hair, it is possible that it existed in other therapsids such as the gorgonopsids and dicnyodonts. But what about mammary glands? This quote, from http://www.ncbi.nlm.nih.gov/pubmed/12751889, makes it seem possible: "Repeated radiations of synapsids produced a gradual accrual of mammalian features. The mammary gland apparently derives from an ancestral apocrine-like gland that was associated with hair follicles. This association is retained by monotreme mammary glands and is evident as vestigial mammary hair during early ontogenetic development of marsupials. The dense cluster of mammo-pilo-sebaceous units that open onto a nipple-less mammary patch in monotremes may reflect a structure that evolved to provide moisture and other constituents to permeable eggs. Mammary patch secretions were coopted to provide nutrients to hatchlings, but some constituents including lactose may have been secreted by ancestral apocrine-like glands in early synapsids. Advanced Triassic therapsids, such as cynodonts, almost certainly secreted complex, nutrient-rich milk, allowing a progressive decline in egg size and an increasingly altricial state of the young at hatching. This is indicated by the very small body size, presence of epipubic bones, and limited tooth replacement in advanced cynodonts and early mammaliaforms. Nipples that arose from the mammary patch rendered mammary hairs obsolete, while placental structures have allowed lactation to be truncated in living eutherians."
So if we travelled back to the Permian, would we have seen gorgonopsids with hair and dicynodont mothers feeding their babies? Either way, the stem-mammals were likely very bizarre.

Bristles and Trunks in Dinosaurs

Art of a theropod with some Gigantoraptors, by Luis Rey (http://www.luisrey.ndtilda.co.uk/)
If you are reading this blog, you should know what dinosaurs are. Dinosaurs first appeared in the Triassic period, and were the dominant terrestrial animals for about 135 million years. Before I go any further, I must add that a dinosaur (called Nyasasaurus) which lived about 243 million years ago
was very recently discovered. If it is a dinosaur, then it is the oldest species known. The dinosaurs are thought to have died out 65 million years ago, although birds are classified as theropod dinosaurs due to the widely held belief that birds are the descendants of dinosaurs. Dinosaurs are classified as archosaurs, which is a clade that also includes crocodilians and pterosaurs.
Some beautiful archosaurs
Over the years that I have researched dinosaurs, one of my favorite things is the paleoart. I especially love the paleoart when it depicts these animals in bizarre yet possible ways. Often, these bizarre representations show the animals with features that you would not expect them to have such as fluffy feathers or massive spikes.

Leaellynasaura depicted as having a covering of fluffy feather! (John Conway http://johnconway.co/)


Paleoart of a sauropod as it dominates a pack of theropods through tail hitting, stomping, biting, and defecating on one (which is a common defense mechanism is modern animals)! YAY!!!!!
(art by Robert Nicholls http://www.paleocreations.com/index.php)
One interesting aspect in recent paleoart of Ceratopsian dinosaurs was the fact that some bristles. That's right, bristles. The discussion of ceratopsian bristles starts with the discovery of a well preserved specimen of Psittacosaurus.
A well preserved specimen of Psittacosaurus
Psittacosaurus were small and hornless ceratopsians from Asia, that lived in the Early Cretaceous period. One fossil Psittacosaurus showed a bizarre feature, what appeared to be bristly or quill like integuments. These bristles were said to be anchored deeply in the animal's skin, 1 mm. wide at their base, likely cylindrical or tubular, and possessed a dark stripe along at least a part of their midline (possibly indicating a hollow lumen). It is thought that the bristles are likely not the same as the filamentous structures or proto-feathers of theropods, as they are oriented differently and do not branch out.

Close up of the Psittacosarus bristle-like structures

An unltraviolet-induced fluorescence photograph of the structures
Although it may seem not as amazing as finding feathers in ceratopsians, these bristles are still interesting as such integuments were previously unknown for ceratopsians. I myself have observed the bristled Psittacosaurus fossil in a museum, and it greatly intrigued me. In fact, I probably spent the most time looking at the bizarre fossil and the accompanying models!
A picture of a model of a bristled Psittacosaurus
  It is unknown what function these bristles served, but scientists have speculated that they may have been used for functions such as display or even used to supported a caudal fin! Tracy Ford and Larry Martin have speculated that the bristle like structures “may have supported a caudal fin that was somewhat analogous to the caudal fin in modern amphibians, such as the Hellbender … and tadpoles”.
In a review of Tracy Ford and Larry Martin's aquatic Psittacosaurus theory, amazing palaeozoologist Darren Naish (who was one of the people who inspired me to make this blog) wrote this:
"They make vague and unconvincing comparisons between the psittacosaurid forelimb and that of sea-turtles, cetaceans and other swimmers, imply that flexible hindlimb joints provide evidence for a swimming habit, suggest that gastroliths may have been present because of a role in buoyancy control, and draw attention to the presence of a laterally compressed tail skeleton and dorsally placed nostrils and orbits."
Koreaceratops, a relative of Psittacosaurus that is also speculated by some scientists to have had a caudal fin

While I personally love the theory, and absolutely adore the idea of a Psittacosaurus swimming around and swallowing stones to control buoyancy, it seems unlikely and not well supported to many scientists.
However, more evidence exists that may support the theory that these bristles were just that. At the Hall of Paleontology at the Houston Museum of Natural Science, there exists the only fossilized Triceratops skin known. Paleontologist Robert Bakker said:
"For scientists, and the museum community, the exhibit offers unique objects, including the only Triceratops skin found to date, a specimen that showed they had been wrong in believing the horned vegetarians had smooth skin. In fact, it had bristles".
Awesome art with Robert Baker in the middle (http://chrismasna.deviantart.com/art/Dr-Robert-Bakker-242454753)


 So straight from the lips of famed paleontologist Robert Bakker, an amazing discovery was revealed. According to him, the fossilized skin shows that the Triceratops had bristles! This statement may seem bizarre, yet a very experienced paleontologist like Bakker should be making accurate interpretations. Its back and tail is reported to have a series of bumps, each one holding a nipple-like structure which likely held bristles. We know that Psittacosaurus, also a ceratopsian, had bristle like structures so it is likely that Triceratops would have had them too!
Beautiful artwork of a Triceratops in its true form, with bristles!
What a beautiful discovery, just imagine a herd of bristled Triceratops on the Cretaceous plains. Of course, we truly have no idea what these bristles were used for. Perhaps, as more ceratopsians are discovered, we will learn more about these strange bristle like structures documented in both Psittacosarus and Triceratops.



Awesome and totally possible art of Sauroposeidon with air sac display structures by Brian Engh
(http://dontmesswithdinosaurs.com/?p=471)
If you thought that learning that Triceratops had bristles really ruined your childhood memories, this idea might be also depressing. However luckily for you, it is only a theory and is disputed by many.
Before I go on to the disputed sauropod anatomy theory, I need to add that the art above depicts a totally possible feature of display air sacs in sauropod dinosaurs. In fact, it may even be likely! Brian Engh supports his art by stating how sauropods had highly pneumatic skeletons. This means that, like birds, sauropods had complex respiratory systems with air sacs and hollows throughout their skeletal systems. Brian states that "When I learned that, I got very excited, because birds don’t just use their wacky respiratory systems for breathing, they also use them for inflating crazy display structures."
A modern relative of sauropods, with a display air sac structure
So, yes it is very possible that sauropods were bizarre animals with huge air sacs. But this is not the weirdest theory about them.
A trunked sauropod.....kidding right? No
Yes, this part is about trunked sauropods. You probably think this is a joke, but don't go yet as you may enjoy this very bizarre section of the article. And yes, there are some scientists who think it is possible. In 1975, Walter Coombs first theorized that sauropod dinosaurs had trunks due to the similarity of size, shape and position of sauropod nostrils to mammals which have, or are thought to have had, a proboscis or at least a very large nose. While this theory of trunked sauropods sounds outlandish, Bill Munns (creature reconstruction and costume artist) actually makes some fairly good (in my opinion) arguments for the theory. In fact, he has produced sculptures depicting a trunked Brachiosaurus and feels that this depiction is accurate.
Munn's model of a trunked Brachiosaurus, with the more conventional Brachiosaurus reconstruction to the far left
(http://www.billmunnscreaturegallery.com/bmcgsite_014.htm)

On his website, where he has included information as to why he feels this theory is accurate, Munns states that the hypothesis derives from the question of why the nostril openings of Brachiosaurids are at the top of these sauropods' skulls. He adds that the only living species with similar nostril structures are whales and elephants. Although sauropods were once thought to have been an aquatic or often semi-aquatic species, this is now widely viewed as not valid and makes comparisons with cetaceans (aquatic animals) invalid. So that leaves elephants, which are also the largest land herbivores of their time.

A Brachiosaurus skull with nostril openings on top and the reconstruction of a trunked Brachiosarus by Munns
 Munns supports his theory by pointing out that the functions of the nose are not advanced or helpful by their placement in brachiosaur.

"1. There is no advantage in placing nostrils at the top of the head with respect to effective breathing. No advantage is conferred by the re-arrangement.

2. No advantage in warming and humidifying the intaken air is gained by the re-arrangement.

3. No advantage in olfactory perception is gained by the re-arrangement.

4. Ability to smell food sources and see what is being smelled is lost in the re-arrangement.

5. Ability to smell other individuals and see who is being smelled is lost in the re-arrangement.

6. The ability to generate sounds is not improved by the re-arrangement."

 Munns also adds that reconstructions of Brachiosaurus with draping skin over their huge nasal openings, ignores the fact that skull openings tend to be filled with organs or musculature.
According to Munns, this is nonsense
While many scientists argue that comparative anatomy is not good evidence for brachiosaur trunks, anothe interesting aspect was pointed out by Munns. In his argument for Brachiosaurus trunks, Munns wrote this:
"Intriguingly, a trunk has considerable need for just such an enlarged space between mouth and nostrils. The trunk becomes a prehensile organ with ability to pick up and manipulate food into the mouth. And it's most powerful muscles are those running on its ventral side (the underside, toward the belly) because these muscles curl the trunk around something the trunk wishes to lift or manipulate. And these muscles, running from tip to skull, need an attachment point on the skull between the mouth and nostrils. Generally, to enlarge a muscle and increase it's power, nature needs to enlarge the surface attachment area. If there is a trunk, enlarging the skull area between mouth and nostril openings in the skull increases that area of muscle attachment, and thus increases the potential for greater size and power of the primary trunk muscles that close around an object and lift it.
So an enlarged space between mouth and nostril openings in the skull argues strongly for a trunk, not simply because it's similar to the elephant's anatomy, but because it is fundamentally advantageous for a trunk on any species. There is no other explanation I am aware of for why a skull with such an arrangement might be so configured."
 Interestingly, this arrangement is what is seen in Brachiosarus skulls.
Munns concludes his analysis with this:
"Other authors, when discussing the prospect of a trunk, especially in brachiosaurus (which has this massive indentation above the maxilla and leading into the nares), these authors cite other explanations for the indentation and what possible organ it might house. Often mentioned are a blood cooling device so the brain is not engulfed in blood too hot, a vocalization device, and an unusually specialized olfactory device. But none of these things argues for why the nares are at the top of the head. None requires a shift in nostril openings into the skull from the standard front facing position. And none of these ideas interferes with or is incompatible with a trunk. You can have any of these, or all three, and still have a trunk. So there is no need to "choose one" to the exclusion of the others. Another argument for the trunk is the simple fact that the creatures are huge, the heads are small, and herbivores need a higher physical volume of food than carnivores because the vegetation has less nutrition, pound for pound, than flesh. This all argues favorably for some assistance in gathering leafy matter and shoving it into the mouth as fast as possible. Given the arms cannot do so, and the tongue can only do so marginally, a trunk would be the most helpful device to feed efficiently"
 
So, in my opinion, Munns gives a pretty good argument for Brachiosaurids having trunks or a form of proboscis. Munns also discussed the possibility of Diplodocids having a trunk or proboscis.
A trunked diplodocid
Diplodocids likely did not have a trunk, however, as the facial nerve in these animals is too small to control an organ like a trunk. It is far more likely that the suggestion of Lawrence M. Witmer, that the nostrils of Diplodocus open at the front of the face, is valid.
(http://www.billmunnscreaturegallery.com/bmcgsite_078.htm)
However, Munns argues that Witmer's hypothesis likely does not apply to Brachiosaurus. He argues that the skulls of Brachiosaurus are unlike any other sauropod skull and are the result of a profoundly different evolutionary influence. He also compares the body structure of brachiosaurids to giraffes, which have a prehensile appendage (their tongues) to gather food.
I find this theory extremely interesting and Munn's argument to be pretty good. However, as with almost all theories, scientists dispute it. Here is palaeozoologist Darren Naish's rebuttal: http://scienceblogs.com/tetrapodzoology/2009/03/20/junk-in-the-trunk/. Sadly, he has some good arguments against Brachiosaurus trunks. However, to me at least, it may still be possible that this bizarre theory is true and that Brachiosaurids did have trunk like appendages. But there is evidence against it still, and it is basically a theory that may never be proven or disproven. Either way, as you have seen in this article (if you haven't given up already), the anatomy of many ancient reptiles was truly very bizarre!

No plagiarism here :), but here's a Works Cited list: