__________The Paleontograph

A newsletter for those interested in all aspects of PaleontologyVolume

_________________________________________________________________

Edited by Tom Caggiano and distributed at no charge

From Your Editor

Welcome to our latest editionweather. The weather here is always changing with sometidifferences.

I made the best find of my collecting career on my annual trip to KS. I came upona complete 17ft long Mosasaur. It was laid out perfectly just sitting there on thesurface. One BIG problem, it had been laying there for a few yeajust about every bone was fractured into pieces and dust. I was able to collect asection of the neck and another of the tail. The rest fit into a few flats. It is aperfect illustration of the fact that fossils that go uncollected turn toSomething the "Lets save the fossils for the future generations" set should learn.Laws set up to protect fossils don't always have the desired effect.

As usual, Bob has served up a varied and well written selection of articles.

The Paleontograph was created in 2012 to continue what was originally the newsletterof The New Jersey Paleontological Society. The Paleontograph publishes articles, bookreviews, personal accounts, and anything else that relates toFeel free to submit both technical and nonrange of people interested in fossils. Articles about localities, specific types of fossils,fossil preparation, shows or events, museum displaywelcome.

This newsletter is meant to be one by and for the readers. Issues will come out whenthere is enough content to fill an issue. I encourage all to submit contributions. It will beinteresting, informative and fun tcontributors want it to be, so it will be a work in progress. TC, January 2012

The Paleontograph________

A newsletter for those interested in all aspects of PaleontologyVolume 7 Issue 2 July, 2018

_________________________________________________________________

Edited by Tom Caggiano and distributed at no charge

Tomcagg@aol.com

Welcome to our latest edition. I hope you are enjoying the warm summerweather. The weather here is always changing with sometime extreme

I made the best find of my collecting career on my annual trip to KS. I came upona complete 17ft long Mosasaur. It was laid out perfectly just sitting there on thesurface. One BIG problem, it had been laying there for a few yeajust about every bone was fractured into pieces and dust. I was able to collect asection of the neck and another of the tail. The rest fit into a few flats. It is aperfect illustration of the fact that fossils that go uncollected turn toSomething the "Lets save the fossils for the future generations" set should learn.Laws set up to protect fossils don't always have the desired effect.

As usual, Bob has served up a varied and well written selection of articles.

The Paleontograph was created in 2012 to continue what was originally the newsletterof The New Jersey Paleontological Society. The Paleontograph publishes articles, bookreviews, personal accounts, and anything else that relates to Paleontology and fossils.Feel free to submit both technical and non-technical work. We try to appeal to a widerange of people interested in fossils. Articles about localities, specific types of fossils,fossil preparation, shows or events, museum displays, field trips, websites are all

This newsletter is meant to be one by and for the readers. Issues will come out whenthere is enough content to fill an issue. I encourage all to submit contributions. It will beinteresting, informative and fun to read. It can become whatever the readers andcontributors want it to be, so it will be a work in progress. TC, January 2012

________

A newsletter for those interested in all aspects of Paleontology

_________________________________________________________________

Edited by Tom Caggiano and distributed at no charge

. I hope you are enjoying the warm summerme extreme

I made the best find of my collecting career on my annual trip to KS. I came upona complete 17ft long Mosasaur. It was laid out perfectly just sitting there on thesurface. One BIG problem, it had been laying there for a few years too long andjust about every bone was fractured into pieces and dust. I was able to collect asection of the neck and another of the tail. The rest fit into a few flats. It is aperfect illustration of the fact that fossils that go uncollected turn to dust.Something the "Lets save the fossils for the future generations" set should learn.Laws set up to protect fossils don't always have the desired effect.

As usual, Bob has served up a varied and well written selection of articles.

The Paleontograph was created in 2012 to continue what was originally the newsletterof The New Jersey Paleontological Society. The Paleontograph publishes articles, book

Paleontology and fossils.technical work. We try to appeal to a wide

range of people interested in fossils. Articles about localities, specific types of fossils,s, field trips, websites are all

This newsletter is meant to be one by and for the readers. Issues will come out whenthere is enough content to fill an issue. I encourage all to submit contributions. It will be

o read. It can become whatever the readers andcontributors want it to be, so it will be a work in progress. TC, January 2012

PALEONTOGRAPH Volume 7 Issue 2 July 2018 Page 2

Why Dinosaurs Matter--A ReviewBob Sheridan October 8, 2017

Who would fail to check out a new book called “WhyDinosaurs Matter.” Not me, so here is my review.The author Kenneth Lacovara is geologist andpaleontologist at Rowan University (New Jersey). Heis best known for discovering Dreadnoughtus, thelargest and most completely known titanosaur (fromArgentina).

I am familiar with TED talks, but I did not realizethere was a series of TED books (about two dozenof them so far) until I saw “Why Dinosaurs Matter”.These books seem to be written counterparts to thetalks. A video of one relevant TED talk by KennethLacovara is:

https://www.ted.com/talks/kenneth_lacovara_hunting_for_dinosaurs_showed_me_our_place_in_the_universe

The book “Why Dinosaurs Matter” is divided into 12chapters, each covering some aspect of dinosaursor fossil life in general:

1. In defense of dinosaurs. While dinosaursdemonstrated adaptability for 165 millionyears, we still use the word “dinosaur” tomean “obsolete”

2. Is a penguin a dinosaur? How to distinguishdinosaurs from other extinct reptiles usingcladistics.

3. Walking museum of natural history. Howevolution depends on history.

4. Fossils underfoot. How people figured outfossils were the remains of ancient life.

5. Deep time. How people figured out how longthe history of life really is.

6. Thunderclaps. Uniformitarianism vs.catastrophism in geology.

7. Making sense of monsters. Earlyinterpretation of dinosaurs.

8. The king. What we know aboutTyrannosaurus, especially concerning itspuny arms.

9. Champions. Extreme dinosaurs.10. Dreadnoughtus. The discovery of

Dreadnoughtus and sauropods in general.11. Dinosaur apocalypse. The extinction of

dinosaurs.12. Why dinosaurs matter. Why studying the

ancient past provides perspective on thepresent.

You can think of this as a collection of essays, whichcan be read in any order. There are someillustrations by Mike Lemanski, but these are purelydecorative and convey no real information.

I am of two minds about this book. It is certainlywritten in a clear, compact, and engaging style(which is expected from TED talks), and it gives agood paleontological and historical perspective tothe lay person, which I am assuming is the targetaudience. On the other hand, for most paleontologyenthusiasts (like most readers of the Paleontograph)most of the material is familiar and the philosophicalbits are preaching to the choir. Most of us alreadyappreciate that the common use of the word“dinosaur” to mean “obsolete” is terribly unfair, andwe realize that studying ancient life is a good way forhuman-kind to learn humility, etc. Admittedly, thereis some material that is new to me, for instance inthe chapter on Dreadnoughtus.

So if you see this book in the library and can read itfor free, go ahead and do it. I would buy it only forsomeone who is not already well-versed inpaleontology.

Sources:

Lacovara, K.“Why Dinosaurs Matter”TED Books, Simon and Schuster, New York, NY,2017, 169 pages. $17 (hardcover)

PALEONTOGRAPH Volume 7 Issue 2 July 2018 Page 3

The Sauropod Dinosaurs--A Review

Bob Sheridan October 22, 2017

Sauropod dinosaurs were colossal; the largest landanimals ever (up to 20 times the weight of a largeelephant, and up to 60 ft. tall). That is reasonenough to be fascinated by them. While there wereother prehistoric creatures with long necks, thenecks of sauropods were longer (up to 8 times thelength of the neck of a giraffe). There is nothingremotely like sauropods today, so it is hard to guesshow they functioned. Making it more difficult forpaleontologists, sauropods were generally so bigthey were hard to bury, and thus individualspecimens tend to be very incomplete. It is veryunusual to find a skull or a full tail.

While I am a dinosaur enthusiast, I generally don’tfollow the literature on sauropods, and I was glad tocome across a popular book on the subject from lastyear “The Sauropod Dinosaurs” by Mark Hallett andMathew Wedel. This contains a contemporarysummary of what is known, or what can bereasonably speculated about, sauropods. MathewWedel is a sauropod expert at the WesternUniversity of Health Sciences department ofanatomy. He is probably best known for hisdescriptions of the dinosaurs Aquilops,Brontomerus, and Sauroposeidon. Mark Hallett is avery well-known paleoartist.

The chapters are:

1. Sizing up sauropods.2. Parting of the ways.3. A sauropod field guide.4. Of Bones and bridges.5. Brontosaur biology: to immensity and

beyond.6. Conifer cuisine.7. A sauropod in the lab.8. The next generation.9. Predator and prey: the ancient race.10. Around the mesozoic world.11. End of eden?12. Summing up sauropods.

The first scrappy sauropod remains discovered inthe 1840’s were at first mistaken for those of a whale(perhaps only because of their size), and even whenidentified as reptilian, the name “cetiosaurs” (whalelizard) stuck. (There is still a “wastebasket” group of

sauropods named Cetiosaurs after the originalspecimen.) The idea that sauropods were aquatic orsemi-aquatic persisted well into the 20th centurywhen they were depicted as wading armpit-deep inswamps, even when the skeletal evidencesuggested that they were fully terrestrial.

The sister group to sauropods is a class of Triassicherbivorous dinosaurs called prosauropods.Plateosaurus (from Germany) is probably the mostwell-known one. Like sauropods, they had smallishheads on the ends of longish necks. However, theywere generally small for dinosaurs (a few tons). Fora long time is has been speculated that theseanimals could be bipedal or quadrupedal dependingon the circumstances. However, analyses of theforelimbs suggested that the neutral position of thehands was “palms-in”, making it unlikely they couldput their hands on the ground. Interestingly,Eoraptor, a turkey-sized Argentinian dinosauroriginally thought to be a basal theropod, is nowthought to be a basal prosauropod.

Although at a superficial level all sauropods lookmore or less alike (giant body, long neck, long tail),there are something like a dozen families that differin the skeletal details: how the toe bones arearranged, how the skull is constructed, how thecervical vertebrae are sculpted, how the tail isdisposed, the presence of armor, etc. In retrospect,the diversity is perhaps not surprising sincesauropods had from the Early Jurassic to LateCretaceous to diversify. This chapter has a very nicesummary of each family and their typical features.One surprise: the titanosaur family, which persistedinto the Late Cretaceous, contain the largest andsmallest known sauropods. One does not hear muchabout dwarf theropods (by “dwarf” one means“smaller than an elephant”), but there are many,mostly from Europe.

The problem of how the sauropod skeleton wasconstructed to maintain enormous bodies and verylong necks can be approached by engineeringprinciples, which are embodied in man-made objectslike suspension bridges and cranes. Make the legsmore vertical and shorten the toes. Make the headsmaller, make the neck lighter by hollowing out thecervical vertebrae, and make the neck more rigid bylengthening the zygapophyses, the bony processesthat extend forward and backward from eachvertebra.

Cont'd

PALEONTOGRAPH Volume 7 Issue 2 July 2018 Page 4

Sauropods Cont'd

Have a “cable” (or two) run along the top of theneck. In this chapter is the discussion of whethersauropods held their necks level with their shouldersor could raise their heads high. Two lines ofevidence could be relevant. One is the “osteologicalneutral position,” that is, if all the bony articulationsare in the middle of their range of motion, one wouldexpect a level or slightly downward tilt of the neck forsauropods like Diplodocus. On the other hand, insome sauropods like Brachiosaurus, the neutralposition seems to suggest an upwardly tilting neck.On the other hand, one expects the horizontalsemicircular canal in the inner ear to be parallel tothe ground most of the time, and this would suggestthat the neck was tilted upward so the head couldremain level. This is true for diplodocids also. Thatis, these two lines of evidence tend to contradicteach other. It is likely that some sauropods like tobrowse low to the ground and some like to reachinto the trees. Could sauropods rear up on their hindlegs to get their heads extra high? Diplodocids havetheir centers of gravity close to the hind legs, so itmight be plausible. In contrast, brachiosaurs hadtheir centers of gravity close to the front legs and socould probably not rear up.

Being a sauropod means you have a lot ofphysiological issues due to your size and long neck.Among them:

1. It takes a long time for nerve signal to gofrom your tail to your brain.

2. You have a tiny brain to control yourenormous body.

3. Your body generates a lot of heat and youhave to lose it.

4. It takes a lot of pressure to pump blood fromyour heart to your brain, which might be tensof feet higher. But if you put your headdown, the high pressure would give you ahemorrhage.

5. Your trachea is very long, and that means alot of “dead space.” Breathing like amammal would just push air back and forthinside your trachea and it would never getoutside your body.

6. You can’t spread your forelimbs apart like agiraffe, so how do you get your head downfor a drink of water.

How sauropods solved these issues is still a matterof speculation. I will relay some of the discussion inthis chapter: For 2, it appears that sauropod brainsare about the correct size for a reptile scaled tosauropod size, so they are not particularly “tiny.” For4, giraffes have a special set of distendable bloodvessels that absorb increased blood pressure; it islikely that sauropods had a similar system. For 5, themost plausible answer is that sauropods breathedmore like birds with a one-way air flow: air goes fromthe nostrils and trachea into air-sacs, then to thelungs, and then out through the trachea. For 6, yourhead would be almost perpendicular to the surfaceof the water. If your nostrils were at the front of yourhead, you couldn’t drink and breath at the sametime. This may be why many sauropods had nostrilstoward the top of their heads.

Conifers were the probably the most common typeof plant eaten by sauropods. This is based on theobservation that conifers were the most abundantplant in the Jurassic and that they could regrowquickly enough. One type of conifer that wascommon in the Jurassic but is went extinct beforethe Paleocene are the cheirolepidiaceans. Theauthors note that this would have made especiallygood sauropod food. The authors speculate that theloss of this subclass of conifer led to local extinctionof certain groups of sauropods. However, for all thediscussion about conifers, there is only one knowncoprolite (from a titanosaur) that provides a directlink between sauropods and conifers. Mostsauropods had very simple teeth, good for strippingleaves off branches, but useless for chewing.Reports of gastroliths in sauropods are no longertaken as proof that such stones were needed fordigestion, and it is now thought that having a big gutwould be sufficient to digest most unchewed plantmatter. Different sauropods probably had differentfood preferences; narrow snouts probably meantselective browsing and broad snouts meant grazing.Microscopic scratch marks on sauropod teeth,presumably made by the food moving past the teeth,are taken as evidence that different types ofsauropods fed at different heights.

Cont'd

PALEONTOGRAPH Volume 7 Issue 2 July 2018 Page 5

Sauropods Cont'd

There is a separate chapter on high-tech (forpaleontology) methods applied to study sauropods(or fossils in general): CT scanning of specimens fora non-destructive way to look inside specimens(particularly to look at the brain and inner ear), bonehistology, 3D computer reconstruction via laser-scanned specimens, computer modeling of stress onbone, and 3D printing.

We now know know a few sauropod nesting sites,the most extensive in Argentina and India. Thesecontain a large number of eggs that by today’sstandards we would consider immense (say 10inches in diameter), probably as large as an egg canphysically get. It is somewhat of a mystery how asauropod, which cannot easily squat because of itscolumnar legs, can deposit a fragile egg on theground from a height of ten or more feet. Some havespeculated that the females had some kind ofextendible tube or “ovipositor.”Current thinking is that sauropods produced a largenumber of eggs and that hatchlings received noparental care whatever. They were on their own assoon as hatched. Probably they scattered into theunderbrush and waited until they were big enough torejoin a herd. Most hatchlings were probably eatenvery soon. To survive, a hatchling would have to goin a few years from weighing a few pounds to manytons. This putative incredible growth rate is similar tothat for modern whales. There is some trackwayevidence that shows both small and large sauropodsgoing in the same direction, but this is not strongenough to tell us whether juvenile and adultsauropods herded together.

Sauropod eggs and hatchlings were probably easypickings for predators. (There is one spectacularfossil of a large snake coiled around some eggs.)But what about the adults? It is sometimes argued,by analogy with elephants, that adult sauropods arewere too large to be attacked by theropod predators,which are at best one-tenth the weight. However,there are a number of ways that smaller predatorscan take down a large prey animal. One strategy is“cooperative hunting”, by analogy with wolves.Another strategy is to bite and run away until theprey weakens from blood loss or infection, byanalogy with the Komodo dragon. Sauropods seemto have developed defenses other than sheer size,which includes whip-like tails, clawed feet, and (in afew cases) clubbed tails and armor. There is fossilevidence of theropod teeth and toothmarks onsauropod bones, but this can imply scavenging, notnecessarily imply predation. The authors do not

mention the Paluxy River trackways in this chapter.For decades this was considered a record of atheropod attacking a herd of sauropods, but thisinterpretation has apparently fallen out of favor.

One chapter discusses continental drift and thetypes of environments one would find in variouscontinents, specifically those dozen or so siteswhere sauropod skeletons are found in abundance.The site most familiar to most of us is Fruita,Colorado, which in the Late Jurassic was a forestedfloodplain and home of Diplodocus, Apatosaurus,and Camarasaurus. Less familiar is the archipelagoof islands representing Europe in the LateCretaceous, home of dwarf sauropods likeMagyarosaurus in what is now Romania.

The “End of eden” chapter speculates on why manyJurassic families of sauropods went extinct in theLate Jurassic, and were replaced by titanosaurs.The authors speculate that “classical theropods”,say diplodocids, went extinct because of theextinction of the cheirolepidiacean conifers.Titanosaurs were most abundant in southerncontinents early on but eventually spread world-wideuntil the extinction of the dinosaurs. One anatomicalfeature of titanosaurs is that they are more wide-bodied than previous sauropods and this is reflectedin their trackways.

In the final chapter the authors outline nine aspectsof sauropods that remain mysteries.

This books is very thoroughly illustrated. While thereare many life-restorations of sauropods in theirenvironment, most of the illustrations are diagramsthat help illustrate scientific points. There are alsoabundant photographs of real fossils.

I can give this book a very high recommendation. Inmy mind, it is in the same class as “Pterosaurs” byMark Witten and “Sabertooth” by Mauricio Anton,both of which I have reviewed for the Paleontographin the past few years. It hits the good middle groundin paleontological writing between a popular workand professional publications. There is enough detailfor a knowledgeable amateur to learn new things,but does not assume a great deal of previoustechnical knowledge on the subject.

Sources:

Hallett, M.; Wedel, M.J.“The Sauropod Dinosaurs. Life in the Age of Giants”Johns Hopkins University Press, 2016, 320 pages$40 (hardcover)

PALEONTOGRAPH Volume 7 Issue 2 July 2018 Page 6

Hundreds of Pterosaur EggsBob Sheridan December 8, 2017

Pterosaurs are flying reptiles from the Mesozoic.They are not, of course, dinosaurs, but may berelated archosaurs. There are some very goodpopular books on the subject. The most recent onethat I have enjoyed (and reviewed for thePaleontograph) is:

Witton, M.P. "Pterosaurs" Princeton UniversityPress, Princeton, 2013, 291 pages. $35 (hardcover).

Today’s story concerns pterosaur eggs andhatchlings. Pterosaur eggs are thought to be morelike modern lizard or snake eggs, having a flexible“parchment-like” shell, as opposed to dinosaur orbird eggs, which have a rigid calcified shell.Parchment-like eggs are not water-proof and woulddehydrate if they were left exposed to the air, soneed to be buried to incubate. Based on modernreptiles, that the eggs are buried does not implyanything about whether there is parental careafterward.

Before relatively recently it was usually assumed bypaleoartists that pterosaurs would need parentalcare after hatching, probably because that is thecase with birds. However, since about 2004 a fewpterosaur eggs were discovered with embryosinside. The fact that the embryos have armproportions similar to that of adults has given rise tothe idea that pterosaurs could fly immediately afterhatching. This is in contrast to modern birds, whichhatch with stubby arms and are incapable of flyinguntil they are older.

Wang et al. (2017) describe over 200 pterosaureggs in a single sandstone block from the EarlyCretaceous of China, of which 16 contain embryonicmaterial. This is truly a “jackpot”, compared to thennumber of previously know specimens. The eggsare ovoid and 2-3 inches along the longest axis.The large number of eggs indicate that they areoriginally from a nesting site, although they arejumbled together in such a way as to indicate they

were probably transported from their originallocation, for instance by a flood.

Despite many being deformed, perhaps throughdehydration (the shell was flexible after all), the eggsare preserved in three dimensions.

The bones within the eggs are disarticulated and noskeleton is complete. They probably belong to thepterosaur Hamipterus, which is a largish (5-11 ft.wingspan) pterodactyloid pterosaur with many longconical teeth. The embryos appear to be of differentsizes, indicating different stages of incubation. Muchof the discussion has to do with the state ofossification of the log bones. Even in the largestspecimens, the leg bones seem more nearly ossifiedthan the arm bones. Plus the skull bones have noteeth. One possible inference of this is that thehatchlings could not fly or feed themselves, andwould require parental care, contrary to previousthought. However, this depends on the assumptionthat the embryos that are observed here were closeto hatching, which is not clear. Also, it depends onthe (more plausible) assumption that teeth andcompletely ossified wings were necessary for thehatchling to live independently.

We must keep in mind that pterosaurs were adiverse group and it is plausible that some typeswere hatched ready to live independently and somenot, analogous to the difference between “precocial”and “altricial” birds.

Sources:

Deeming, D.C.“How pterosaurs bred.”Science 2017, 358, 1124-1125.

Wang, X.; Kellner, W.A.; Jiang, S.; Cheng, X.; Wang,Q.; Ma, Y.; Paldonia, Y.; Rodrigues, T.; Chen, H.;Sayao, J.M.; Li, N.; Zhang, J.; Bantin, M.; Meng, X.;Zhang, X.; Qiu, R.; Zhou, Z.“Egg accumulation with 3D embryos provides insightinto the life history of a pterosaur.”Science 2017, 358, 1197-1201.

PALEONTOGRAPH Volume 7 Issue 2 July 2018 Page 7

Halszkaraptor: a Weird Kind ofDromaeosaur

Bob Sheridan December 28, 2017

Dromaeosaurs are the closest branch of theropoddinosaurs to true birds. The evidence suggests thatthey were all feathered. A paper by Cau et al. (2017)describes an unusual specimen of dromaeosaurfrom the Late Cretaceous of Mongolia (75-71 Myr.)preserved in three dimensions in a block of orangesandstone.

This specimen (now called MPC D-102/109) has aninteresting history. It was poached from Mongolia,and passed through the hands of several dealersand collectors, the last of which is Francois Escuillie.In 2015 it was shown to paleontologist PascalGodefroit at the Royal Belgian Institute of NaturalSciences, and CT-scanned at the EuropeanSynchrotron Radiation Facility. CT-scanning wasdone because some of the specimen is stillembedded in rock, and also because it is nowcommon practice to CT-scan unusual fossils to besure they are not “chimeras”, i.e. fakes assembledfrom more than one specimen. (Since rock is verydense, one needs a very intense source of x-rayssuch as produced in Synchrotron facilities.)Arrangements have been made to return thespecimen to Mongolia.

The specimen is given the name Halszkaraptorescuilliei (after Polish paleontologists HalszkaOsmolska who named a closely related species,“robber”, and Francois Escuillie who returned toarranged to return the specimen to Mongolia). Theskeleton is essentially complete. In life, the animalwould be the size of a duck. It has a very long neckand tiny arms. The skull is very duck-like in shapeand contains very numerous (more than expectedfor any theropod dinosaur) tiny teeth.

Phylogenetic analysis places Halszkaraptor at thebase of the dromaeosaurs. It is similar to other

previously named, much less completely known, butmore conventional-looking dromaeosaur generasuch as Mahakala and Hulsanpes. Cau et al. do adetailed analysis of the arm bone proportions ofHalszkaraptor and compare them to those varioustypes of birds and dinosaurs. The conclusion is thatHalszkaraptor probably lived an aquatic lifestyle,using its feet to push against the water, using itsarms to steer, and using its neck to catch prey. Thisis very unusual for dromaeosaurs, which are thoughtto be either ground runners or possibly tree-dwellers. There is only one other dinosaur,Spinosaurus, thought to have an aquatic lifestyle.

The authors do not mention it, but to me the longneck, powerful legs, numerous tiny teeth, and tinyarms of Halszkaraptor are very reminiscent ofIchthyornis and Hesperornis, toothed flightless birdsfrom the Cretaceous of Kansas. (The birds arebigger than Halszkaraptor--about swan size--andhave no tail.) The birds are assumed to be diversafter fish, much like the modern cormorant.

Sources:Cau, A.; Beyrand, V.; Voeten, F.A.E.; Fernandez, V.;Tafforeau, P.; Stein, K.; Barsbold, R.; Tsogtbaatar,K.; Currie, P.J.; Godefroit, P.“Synchrotron scanning reveals amphibiousecomorphology in a new clade of bird-likedinosaurs.”Nature, 2017, 552, 395-399.

PALEONTOGRAPH Volume 7 Issue 2 July 2018 Page 8

Most Primitive Trilobite Eye?Bob Sheridan January 5, 2018

Trilobites are the oldest known animals with well-preserved eyes and these show up in the EarlyCambrian. Trilobite eyes superficially appear muchlike the “compound eyes” in modern arthropods. Asmall digression is in order. Compound eyes areshaped like part of a sphere, but they are made ofmany (sometimes tens of thousands) long, thin,cone-shaped units called ommatidia (singular:ommatidium) that are packed closely together. Thewide part of the cone points to the outside world andthe narrow part of the cone is close to the center ofthe eye. It is usually assumed that, from theviewpoint of the arthropod, one ommatidiumgenerates one “pixel” of the image they perceive.

Going from the outside to the inside, eachommatidia (singular ommatidium) consists of:

1. a lens2. a crystalline cone3. 5 to 12 sensory cells arranged around a

central axis called a rhabdom.

The lenses are visible from the outside as the“facets” of a compound eye. In trilobites, the lens ismade of the mineral calcite, and so is very wellpreserved in fossils. In modern compound eyesthere is usually pigment on the outside of eachommatidium to prevent light leaking between them,i.e. so the ommatidium “sees” only what is directlyaligned with its long axis.

Seeing anything other than the outside of thetrilobite eye in fossils is rare, and until fairly recentlynothing was known about the interior structure. In2013 Schoenemann and Clarkson used highresolution CT scanning to examine cross-sections ofthe eyes of a number of trilobite fossils from threeDevonian genera: Geesops, Barrandeops,Chotecops. For Geesops, one sees in a cross-section through the upper third of the compoundeye, a series of "rosettes" about 500 micrometers indiameter with a star-shaped inner core surroundedby six or so wedge-like shapes. Barrandeops issimilar except that the rosettes are about 200micrometers in diameter, and there are up to twelvewedge-like shapes around the central core. The onespecimen of Chotecops has the outermost surfaceof the eye broken so that one may see the shapesbelow the surface. The rosettes presumablyrepresents the cross-section of the sensory cells. Insize and in having a central cell with a star-shaped

cross-section they most resemble the ommatidia ofthe horseshoe crab Limulus, in particular. This is notsurprising given that both are considered primitivechelicerates. So, by the Devonian (~400Myr), it isclear that trilobite eyes were essentially moderncompound eyes.

Recently Schoenamann et al. (2017) studied a verymuch older trilobite: a specimen of Schmidtiellusfrom the Early Cambrian of Estonia (<500Myr).Schmidtiellus is a short (about the same length aswidth) trilobite a few inches long. One importantaspect of this particular specimen (which happens tobe the holotype) is that it is preserved as calciumphosphate, which in other Cambrian specimenstends to keep a lot of detail. Another is that botheyes are abraded so that one may see the internalstructure. In particular, one can see individualommatidia in cross-section with a microscope.Schmidtiellus has fairly simple eyes for a trilobite,with only about 100 facets per eye. There are twounexpected features of the ommatidia ofSchmidtiellus. First there does not appear to be aseparate lens. Second, the ommatidia do notactually touch each other, as they would in a moderncompound eye. There are two implications of this,that the eyes could not form a continuous image,and that there did not have to be pigment to keepleaking between the ommatidia.

Certainly one can conclude that the basicanatomical features of compound eyes developedvery early, but what about the details? Theassumption is that Schmidtiellus has eye featuresthat represent the primitive state of all trilobites.However, given that there is only one specimen ofvery early trilobite in which the structure of the eye isvisible, it is hard to eliminate the possibility that itseye features are peculiar to that one group oftrilobites.

Sources:

Schoenemann, B.; Clarkson, E.N.K."Discovery of some 400 million year-old sensorystructures in the compound eyes of trilobites."Scientific Reports 2013, 3, 1429.

Schoenemann, B.; Parnaste, H.; Clarkson, E.N.K.“Structure and function of a compound eye, morethan half a billion years old.”Proc. Natl. Acad. Sci. USA, 2017, 114, 13489-

13494.

PALEONTOGRAPH Volume 7 Issue 2 July 2018 Page 9

Caihong: The Jurassic Dinosaurwith Iridescent Plumage?

Bob Sheridan January 17, 2018

China has produced many dozens of exquisitelypreserved feathered dinosaurs, most of them fromthe Early Creteaceous, but some as old as theMiddle Jurassic. Hu et al. (2018) describe a newtheropod specimen from the Tiaojishan Formation(~161 Myr.), which they have named Caihong juji(“rainbow big crest”). This specimen is nearlycomplete and has clearly preserved plumage onbody, arms, and legs. In life the specimen, althoughprobably an adult, would be only 16 inches fromnose to tail, smaller than Microraptor, which isconsidered a very small theropod.

Caihong is more or less similar to most small bird-like theropods (e.g. Archaeopteryx, Anchiornis,Microraptor, Xiaotingia, etc.) in the skeletalcharacteristics: large eyes, long legs, long arms,long tail, pointed snout with many small teeth. Oneunusual feature for bird-like theropods is that there isan additional small process pointing up dorsally fromthe lacrimal bone. This is the “crest” mentioned inthe title of the paper. (The authors call it “prominent”,but this crest sticks out only a tiny fraction of theskull length; it might not even extend past the layerof feathers on the head.)

Caihong has very long feathers on its arms, tail, andlegs in which much detail is preserved. These clearlyhave asymmetrical vanes, and are therefore “flightfeathers.” Caihong is the earliest example of ananimal with asymmetrical feathers and very longforearms. Caihong joins the small set of feathered

dinosaurs that appear more flightworthy thanArchaepteryx, but lived 10-6 Myr. earlier. Theauthors tentatively identify some slender feathersnear the thumb of Caihong as analogous to thealula, which are feathers attached to the thumb inmodern birds.

Most of the headlines attached to Caihong have todo with its proposed coloration. If you have beenfollowing the paleontological literature for the pastseven or eight years, you will know thatmelanosomes are often preserved in fossil feathersand are visible by scanning electron microscopy.Microsomes are microscopic bodies that containpigment. In modern animals, including birds, the sizeand shape of melanosomes is correlate with the typeand color of pigment. Different types ofmelanosomes may appear on different parts of thesame feather. The assumption is that one can usethe size and shape of fossil melanosomes toestimate the color of the feathers of extinct birds anddinosaurs. (One possible complication is that thesize may change during fossilization.)

In the case of Caihong, the authors examined thepreserved feathers from 66 sections around thefossil, particularly the head, back, and tail. Themicrosomes found therein are described as “platelet-like” and stacked in layers. The modernconfiguration of melanosomes most like this is onthe iridescent throats of some hummingbirds.Rainbow-like iridescence is produced by thediffraction of visible light by closely-spaced layers,much like a diffraction grating. The exact nature ofthe pigment does not matter as much to the color.The authors suggest Caihong is therefore agenerally black dinobird with iridescence (hence the“rainbow” in its name).

In popular accounts Caihong is reconstructed as ablack feathered dinosaur with iridescent blue andgreen feathers on its head and neck. Very striking,but not what the authors of the paper aresuggesting.

Sources:

Hu, D.; Clarke, J.A.; Eliason, C.M.; Qiu, R.; Li, Q.;Shawkey, M.D.; Zhao, C.; D’Alba, L.; Jiang, J.; Xu,X.“A bony-crested Jurassic dinosaur with evidence ofiridescent plumage highlights complexity in earlyparavian evolution.”Nature Comm. 2018, 9, 217.

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from Indiana University Press on September 11,2017. The digital version is already available from

The second edition is updated with newinformation on fossil discoveries and additionalbackground on the history of paleontology inKansas. The book has 427 pages, over 200 colorphotos of fossils by the author (including TomCaggiano’s dinosaur bones in hand shot), is printedon acid free paper, and weighs in at a hefty 3.6

A review from Copeia....

“Oceans of Kansas remains the best and only bookof its type currently available. Everhart’s treatment ofextinct marine reptiles synthesizes source materialsfar more readably than any othernontechnical book-length study of the subject.”—Copeia

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“Oceans of Kansas remains the best and only bookcurrently available. Everhart’s treatment of

synthesizes source materialsfar more readably than any other recent,

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