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Note: this thread should be viewed as a thought experiment, not necessarily fact. I am still too new to these concepts to put my foot down yet, but enjoy mentally turning them over A paleontologist at his core is an evolutionary biologist. The goal of an evolutionary biologist is to study the dynamics of evolution, and not just "species" for their own end. After all, the concept of a species only exists as a man made construct that humans use to pin down certain moments in the path of change in lineages. Where one decides to put way points (species) in that gradient doesn't matter, so long as there are at least two way points there so that comparisons can be made. If that was confusing, forget what I said for now and consider this: Animals change from one to another through cumulative steps and changes. Under textbook conditions, the graph of change from species to species is a smooth slope, not stair steps. To illustrate this point, consider the color gradient below. This gradient represents a change from one animal (blue) to another animal (red). Humans assign names to color the same way we assign species to animals. Artificially. At the top left, the image is blue. At the bottom right, the image is red. Now, at what exact point on this image does blue change to red? We can never know- there is no answer. Such a change is too gradual to point to one spot and say "now the blue just turned to red". But, to make sense of the change, we can point to the middle phase and call that phase "purple". "Purple" is simply a way marker we put down to digest the change of blue to red. I could have put such a way point down anywhere in that gradient, said "that's the moment of change!" and been equally right. As a society, we've just decided the arbitrary "purple" point is where we'll dig in, so that we may have a consensus. The same idea applies to the gradient of animal change. There's no point where one animal suddenly becomes the next, we just assign points in that gradient and call each point a "species" for our own sanity, to make sense of change. BUT! Here's the thing: In paleontology, we do not have the curse of a perfectly filled out gradient, with every animal that's ever lived represented as a fossil that can be easily traced from one to the next. We do not really "choose" our way points. We're forced to use the few animals that fossilized as way points, to fill in the gradient because they're the only data we have. I guess that makes the paleontologists job easier. For example, we know that the mosasaur Clidastes, by virtue of it simply existing, is a way point in it's respective spectrum. We can tell that the mosasaur Mosasaurus is a further developed way point in that spectrum. There are no fossils in between them, so we physically can't assign a metaphorical "purple" in between them, but then Jormungandr is discovered, and now we can. Thus, we were forced to use Jormungandr as our way point to define the Clidastes---->Mosasaurus change. ----------------------------------------------------------- This is the inherent flaw of the "missing link" argument. No one "missing step" exists between two species. Since change is gradual, one can divvy up a perfect gradient into 1000 steps and each will still be slightly different from each other. It's a game you will play for infinity. When working with fossils, you're lucky to find one step in between two others, and so when you do, that's the representative of change you're forced to acknowledge. Now, such a gradient only considered the change from the blue species to the red species. In real evolutionary environments, this gradient branches off in many directions, changing to all sorts of wonderful colors, from greens to yellows to blacks and whites. I chose the two color gradient for ease of concept. Now that we understand that way points are artificially planted in a perfect gradient, we can understand the core of phylogenetic technique. Putting just one point down in this below gradient is useless. We have nothing to compare it to, no way to quantify change. If I put two points down though, NOW I have a way to quantify change. I can say with authority that point B is more red than point A, or vice versa. _______________________ This is what "out-groups" exist for in phylogenetic analysis. An out-group is an animal that you can point to say "this animal represents the most primitive version of the group I'm interested in". The out-group is your anchor of comparison - without it, you would be trying to understand the rest of the group in a vacuum. To say "Clidastes-like mosasaurs evolved forwards, turning into Jormungandr-like mosasaurs and then to Mosasaurus-like mosasaurs" is an empty statement unless you decide on a primitive group first to enable such comparisons to be made. Among mosasaurs, the primitive condition is what's seen in land lizards like Varanus (monitor lizards). NOW I can argue that "Clidastes is most like the primitive Varanus, making Clidastes most primitive mosasaur in our group of three, and from there, Jormungandr is next, and then Mosasaurus is least like Varanus of the three, making it the most derived. So, if you want to understand change in any animal (in my case mosasaurs), you must understand the usual out-group (in my case Varanus). If you know the states of the skeleton in Varanus, you know the anchor to make comparisons off of. -The more your mosasaur of interest looks like Varanus, the less change it experienced and thus the more primitive it is. -The less your mosasaur looks like Varanus, the more change it had to undergo to accomplish that, so the more derived it is. Easy peasy. (note: this gets more complicated sometimes - derived animals can also evolve back into primitive traits. But don't worry about that for now) So, if you're interested in mosasaurs, look at Varanus. I fortunately found the absolute bible of Varanus anatomy today - I was so delighted I felt instantly obligated to make this post. Illustrated skeletal elements in great detail and descriptions of its morphology and physiology. This is invaluable to those interested in any lizards. Enjoy! https://www.notesonzoology.com/vertebrates/varanus/skeleton-of-varanus-with-diagram-vertebrates-chordata-zoology/8396

In an anatomical discussion - Are there any extant "ornithshian" species? If not, did any "bird-hipped" species survive the K/T extinction?

Greetings. I would like if possible a visual guide to understand the difference between Odontochile and Zlichovaspis, which most often get mistaken with each other. I have red the differences, but without a visual aid I am struggling to understand them.

So...I have some questions about sclerotic rings. In addition to supporting large eyes, resisting pressure, etc. how do they work? I ask as I see four basic forms across species, extant and extinct. the first is a fixed ring fused to the frontal and zygomatics. the second looks to be a fused or partially fused ring that is around the iris the third is a ring of small plates held together by connective tissue and the fourth looks like a camera iris Where my confusion arises is with the third and fourth and some birds and fossils. Do these function as part of the actual muscles of the iris sliding/flexing the sclera, or are they purely support for the overall structure? For those unfamiliar:

There are a lot of experienced dinosaur collectors out there but for the newbie I thought a topic on the anatomy of bones and teeth would be beneficial, in plain english. Avoids reading pdf's that are difficult to get through the technical terms. Orientation Skeleton The specific sketal structure of a dinosaur varies between theropod and herbivore but the major elements are typical. Skulls of dinosaurs are not comprised of a single bone but many elements See the osteology of a Trex skull on page 2 The holes in the skull are identified as follows Theropod Teeth Theropod teeth are widely collected let's look at their anatomy and nomenclature Tooth Orientation Apical- The direction from the cervix to the apex (Fig. 1C, E). Basal- The direction from the apex to the cervix (Fig. 1C, E). Mesial- The direction towards the jaw midline, center (Fig. 1C). Mesial can refer also to the surface facing the jaw midline, center. Distal- This term is used slightly differently for teeth versus denticles. For teeth, distal refers to the direction away from the jaw center and towards the posterior end of the jaw (Fig. 1C). For denticles, distal refers to the direction away from the crown, from the denticle base to the denticle apex (Fig. 1E). Proximal- From the denticle apex to the base, proximal refers to the direction towards the crown ( Fig. 1E). Labial- The surface or direction pointing from the skull outwards, thus towards the lips or cheeks ( Fig. 1D). Lingual- The surface and direction towards the skull midline, thus facing the tongue ( Fig. 1D). Tooth Situation and Position Isolated Tooth- Tooth shed or non-articulated with the toothbearing bone. This is what collectors typically purchase. Shed Tooth- Tooth lost while alive,, either falling out due to the eruption of the replacement tooth or when processing food (e.g., biting, impaling, shearing, chewing), and therefore only preserving the crown and the basal-most part of the root. In Situ Tooth-Tooth within the alveolus of the tooth-bearing bone. Erupted Tooth- Tooth that grew outside the tooth-bearing bone, thus fully visible in the mouth. Unerupted Tooth- Tooth within the alveolus and still inside the jaw, and therefore not visible or only partially visible in the mouth. Premaxillary Tooth - Tooth in front of the upper jaw, typically four would exist in a theropod Maxillary Tooth - Tooth in the upper jaw that follow the Premaxillary teeth. Dentary Tooth- Tooth in the lower jaw Tooth Anatomy Crown (co) Portion of the tooth covered with enamel, typically situated above the gum and protruding into the mouth Root (ro) Portion of the tooth beneath the gum and embedded in an alveolus or an open alveolar groove

hi i try to reconstruct a spinosaurus skeleton, i miss some bones of course, lot of bones ares in privates collection,and it s difficult to access them. my idea is : if you have in your collection some cervicals vertebrae or dorsals , the size is not a problem, i look for 3D models of them. i look also for the 3D models bones of the front limbs. thanks for help in this project.

After looking at different pictures of ammonites for a hot minute this burning question hit me. I know that some ammonites have a greater number of whorls from keel to umbilicus than others, but which ammonites have the most/least number of whorls in their shells from keel to umbilicus? I haven't yet found any satisfying answer in my own searches and I know this is gonna be one of those questions that keeps me up at night.

Hello, I just purchased this interesting-looking partial Gonioceras "internal cast" fossil originating from Rock County, Wisconsin. I had some questions regarding the anatomy of this specimen: (EDIT: I forgot to mention dimensions; the rock is about 9cm x 8.5cm) 1. From a quick internet search (https://equatorialminnesota.blogspot.com/2016/02/gonioceras-when-nautiloid-is-also.html) it seems the lateral edges of the shell chambers curve away from the body as the shell tapers towards the tip. From this information, in this photo of my specimen would the tip/apex be towards top-right and body towards bottom-left? 2. Toward the top-right of my specimen, there appear to be exposed cross-sections of portions of the apical chambers. Here I see holes aligned at the center of the chambers looking as if a narrow cylinder passed through them. I'm thinking these are the holes that the siphuncle went through in the animal. Is this a reasonable assessment? 3. I read that Gonioceras siphuncles are described as being "sub-central". Judging by the position of the putative "siphuncle holes", would that mean this photo of my specimen is looking at the ventral surface of the animal's shell? Or is this too much to infer from this specimen? Thanks!

Hi! I got this Hadrosaur caudal vert from the two medicine formation. in Pondera County. I was wondering what part of the tail this bone would have come from? the seller says it is likely a proximal vertebra, but couldn't give any details on its placement. Is there any possible way you can tell what part of the tail this fossil belonged to? assuming a grown individual of the species. If exact placement isn't possible, Ill settle for general region. The centrum of the Vert is 2.7 x 2.3. x 2.2" and the process is 7.6" long in a straightline including the anterior points of articulation. As always I can provide more detailed pictures/measurements of requested parts of the specimen.

I've seen people collecting Megatherium claw cores on this site for a good while, but I never did get a good look at what a complete claw would look like (since judging by the fact that they're cores, there'd have to be more to those claws in life). What other components would make up the claws of animals like Megatherium, and what would a complete claw look like?

Hello together, I am not entirely sure if the fossil ID section is the right place for this, but I am hoping for information on a fossil specimen, its not one I hold in hands, but a ct scan, and I think I may not post pictures because they are copyrighted. While looking for new inspirations for my model building I took a close look at this wonderful ct scan of a Simosuchus clarki skull. A pugnosed crocodile, how sweet is that? I wonder two things: -how is that bilateral bone called that in many crocodiles protrudes downwards from the skullbase reaching between the mandibles? -Could the fragile structure of the distal end of said bone hint at a juvenile animal? In recent croc skulls I have seen these bones seemed quite solid. The species description says several specimens in a range of sizes have been found, all below one meter and considered fully grown. on the Digimorph site there are videos showing rotation and cross-sections, the structure in question is best visible in the "roll"-vid: http://digimorph.org/specimens/Simosuchus_clarki/ Thanks and Regards, J

This is the most recent complete list of trilobites described with appendages. Six trilobites have a complete record of the antennae and post-antennal limbs. table from: Zeng, H., Zhao, F., Yin, Z., & Zhu, M. (2017) Appendages of an Early Cambrian Metadoxidid Trilobite from Yunnan, SW China Support Mandibulate Affinities of Trilobites and Artiopods. Geological Magazine, 154(6):1306-1328 PDF LINK

Analysis of anatomical changes and Neck angle https://www.nature.com/articles/s41598-020-63439-0

Hi I was wondering if anyone could help me identify some of the key anatomical features of the calyx of this crinoid (Apiocrinites elegans) and any anatomical features of this brachiopod (specimen unknown). I have trawled and searched but am having limited success so thought there might be a fair few people that would be able to lend a helping hand on here! cheers mark

Hello evereybody, I dont know if this is the right place to post this but I would be interested to learn more about mosasaur skull three-dimensional anatomy. Do someone know where it is possible to buy accurate mosasaur's skull cast? I am looking for something more educational than decorative and ideally not too big. I know that there are plenty of interesting stuffs on the web but from my experience in human medecine nothing is as good as a three-dimentional model to understand complex anatomical structure like the skull. Thanks for helping!

New detail of internal structure of trilobite eyes and implications of their location on the tree of life. https://www.nature.com/articles/s41467-019-10459-8

Hi all, Need a little help identifying this bone from Bracklesham, UK. It measures about 1 inch long, should be Eocene age. Thanks in advance. Jay

7 ft tall Three toed tracks Walks flat on its feet, not on the sides of its feet Three fingered claw marks Osteoderms in skin Ancestor of cloepus, not bradypus Found in North America (do any known ground sloths have a smaller tail or even no tail at all?)

I've always wondered what the 5 radial stripes on echinoids we're and what they do. Any urchin/sand dollar experts know? Polished Echie with the "stripes".

This was a really cool museum. I especially liked their selection of fish and marine reptiles. They also sported a largely complete tyrannosaurus skeleton, an Ammonite five feet tall and four feet wide, and a large completely intact mammoth. Pelagosaurus Typus A Mary Anning Icthyosaur (Two more were present) Plesiosaur Eryops A large fish (One of the Many on display) A perfectly preserved Crinoid The nicest ammonite (My opinion) Perfect spiral pattern And much more that we didn't get photos of........

Hi all! Under the presumption these are echinoderm I've been searching for anatomical features, particularly disarticulated crinoid and archaeocidaris of which both are plentiful in the matrix. In my searching I've been unable to find anything that even remotely resembles these pieces. Any input is much appreciated. Plattsburg fm. - Hickory Creek sh. I attached a group photo of some of them I found, followed by 4 select specimens showing each side front and back. For scale, field of view is ~1cm. Group shot Front Back Front Back Front Back Front Back Thank you all!

My name is Rick, and of course just signed up. First and foremost, I apologize for my pretentious-sounding user name, but I tried several permutations of my name, but all seemed to be taken, and so I gave up in frustration and just used the nickname that people have given me. I'm an evolutionary biologist, a retired Dean and Professor from the University of Massachusetts at Amherst. I stumbled on this site because, for the past few months, I've been consulting on an extensive, old private collection, dating back to the 1950s, that was bought by a local science and education store. I've been identifying, or verifying the identifications, of many hundreds if not thousands of fossils of every imaginable type, and, of course, determining fair market prices. And so, during my 'net surfing, I was directed to The Fossil Forum on several occasions, and became intrigued. And here I am. I may ask your collective advice at times regarding the identification of various items, and may on occasion just post a photo or two that some people might find interesting. I've got a load of them. This collection is truly astonishing.

The National museum of Natural History in Paris, France is absolutely fantastic and anyone with even a passing interest in palaeontology or the natural world should have visited this museum at least once in their lives. It's truly a sight to behold. The museum consists of three buildings and a botanical garden. The first building is the Great Gallery of Evolution. This contains a vast array of stuffed animals. they also have a few specimens of extinct animals like the Quagga and the Tasmanian Wolf. Deep sea creatures Tasmanian Wolf or Thylacinus cynocephalus Equus quagga quagga There is a lot more to see in this gallery but I don't have many more interesting pictures. The second building is the Gallery of Mineralogy and Geology. But I haven't actually entered this building, so I don't have any pictures of it. What makes this museum complex really special though, is the Gallery of Palaeontology and Comparative Anatomy. Photos do not do it justice by a long shot, you need to see it for yourself. To begin with, the hall has wonderful architecture and is really well lit. This is where they keep all the skeletons and fossils. The ground floor contains skeletons of modern animals. The thing is, that there are hundreds of skeletons there to see. This is the best place for studying comparative anatomy. A really cool half Elephant's skull so you can see inside. And now on to fossils...

Hi. I need some help to identify a carpal bone. The label says it is a carpal bone, though I don't really know. It belongs to an otariid, maybe Thalassoleon mexicanus, from the Almejas Formation of Cedros Island, Baja California. I need to know if it's a triquetral, pisiform, trapezium, trapezoid, capitate or hamate bone. I'm so confused I hope the pictures help, but if you need better ones let me know. Thank you.

Hello, As I am starting to get into vertebrae specimens, I have had a hard time finding a good book with a focus on Dinosaur anatomy. I am looking for something that covers a wide range of specific species, with detailed skeletal drawings and descriptions. I always see pictures of these really well done drawings of individual bones that people tend to reference when trying to indentify something. What books do those come from and where can I get them? Every book I have so far has just a life model of the species and then a basci skeletal outline with no where near enough detail to try and identify individual bones. Any suggestions would be great!