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Oxytropidoceras posted a topic in Fossil NewsWhen Did Fish Learn to Walk? Antarctica May Hold the Answer Eric Niilen, Wired Science, November 21, 2018, https://www.wired.com/story/fish-learn-to-walk-antarctica-evolution-tetrapods/ PDF files about papers about tetrapod evolution can be found at: Edward B Daeschler https://www.researchgate.net/profile/Edward_Daeschler/research Adam C. Maloof https://www.researchgate.net/scientific-contributions/15584512_Adam_C_Maloof Yours, Paul H.
Hey everyone You guys might already know about this, but since this fossil is so wonderful, I decided I'd share this paper on TFF (it's kind of old news, but it's a really fascinating find). The paper describes a xenacanth shark (Triodus sessilis) with two temnospondyl tetrapods (Cheliderpeton latirostre and Archegosaurus decheni) as gut content. One of those temnospondyls had ingested an acanthodian fish (Acanthodes bronni) which is also preserved in the fossil. Basically, a "fish in an amphibian in a shark". The specimen was collected from the Permian of Lebach (southwestern Germany). Here's the paper. Enjoy Kriwet et al. 2008 Fossilised 3-level trophic chain.pdf
a book review of: "Earth Before the Dinosaurs" written by Sebastien Steyer; illustrated by Alain Beneteau; translated by Chris Spence. Indiana University Press. 182 pages. Suggested retail: $35.00 USD. In the past twenty years a number of fossil discoveries have illuminated several steps of a key transition in the history of vertebrates: when they first crawled out of water and took on the gravity of life on land. Paleontologists have been sorting through the remains of a growing diversity of Devonian-age fish-like amphibians and amphibian-like fishes across a time when biologists have gone beyond just questioning traditional categories in classification, focusing on a more precise method of determining degrees of ancestry throughout the tree of life. "Earth Before the Dinosaurs" attempts to provide the layman with a guide to the early history of tetrapods, the vertebrate family tree that includes one branch of bony fishes plus all amphibians, reptiles, mammals, and birds. It arrives in the wake of other recently-published books on the subject: the second edition of Jennifer Clack's 2002 "Gaining Ground" (a more technical review of early tetrapods), which was published earlier this year; Neil Shubin's 2008 nonfiction bestseller, "Your Inner Fish," which traced the origins of basic human anatomy down to Devonian-level adaptations and Carl Zimmer's 1998 "At the Water's Edge." Sebastien Steyer wrote the original French text under the title "La Terre avant les Dinosaures." He is a paleontologist specializing in Paleozoic amphibians at the National Museum of Natural History in Paris. Chapter 1 defines basic terms and spotlights the oldest known tetrapods. In a few cases animals familiar to the longtime paleo-enthusiast are revealed to have been reinterpreted to different degrees in recent years. For instance, decades ago, the "lobefin" Eusthenopteron was considered a fish that walked on land, occupying an intermediate stage between fishes and amphibians. Today, however, tetrapod researchers see it as a wholly-aquatic fish not directly related to amphibians. Chapter 2 explains the multi-stage development of limbs in modern vertebrate embryos with notes on how genes play a role in the process. The reader learns how some individuals can be born with incomplete limbs and why some bear an extra digit or two. Chapter 3 samples various groups of Paleozoic (and some Mesozoic) amphibians, though by this point in the book, Steyer has already pointed out that long-established terms like "fish," "amphibian," and "reptile" are no longer precise enough for defining evolutionary relationships. They remain useful as general groupings in broader discussions of diversity, distribution or extinction but too many groups known to have separate ancestries had been shoehorned into the same traditional class because of some shared superficial structures. Today, scientists sort through the full set of known anatomical characters in a given taxon in an effort to isolate only those that link an ancestral group to all its descendants. Chapter 4 reviews early amniotes, lineages that have led to traditional reptile groups (and by extension to mammals and birds), a few still living but most extinct. Steyer discusses amniote origins and how the group was affected by the mass extinction that occurred at the end of the Permian Period. He also notes some unusual Triassic forms. Chapter 5 looks at the work of modern paleontologists, informing the reader on how they have learned to extract more information from past discoveries even as they continue to bring home more fossils from the field. The book is off to a good start with Chapter 1 sorting out the early tetrapods as they are now understood. A handy chart on page 26 places the various genera in time, locality, and paleoenvironment. I liked Chapter 2 for its review of how embryology is connected to paleontology and Chapter 3 informs the reader on how incredibly diverse the tetrapods were during the Paleozoic Era. The reader also gets an education in how difficult it can be for researchers, often working with fragmentary remains, to determine which groups led to modern amphibians, which ones were more closely related to early amniotes, and which ones were simply offshoots that dead-ended during the Paleozoic. As a side note, fans of J.R.R. Tolkien may pick up on an intentionally-humorous passage in Chapter 3. However, it is in Chapter 4 that the level in coverage seems to drop off. I noticed it at the first mention of the synapsids, the technical name for a group formerly known as "mammal-like reptiles." The most famous early synapsid, Dimetrodon, is noted in the text along with some nice illustrations but most of the information on it is found in a caption in the margin. Relatively little text is devoted to Permian synapsids (pelycosaurs and therapsids) despite the fact that they include the dominant carnivores and herbivores across the entire period. I expected more to be said about the first "sabertooth" carnivores on earth. Steyer does include about one page of text on Triassic synapsids, one group of which is noted to have been ancestral to mammals. Chapter 5 is an interesting behind-the-scenes look at the tools of the paleontologist trying to deduce behavior from bones, tooth marks, footprints, and burrows. Translating a book from one language to another is always problematic. Idiomatic expressions and creative metaphors often defy a word-by-word breakdown so any poetry in the original writing can be only approximated if not destroyed. A paleo book can be easier to translate (more literal) than a novel as many technical terms are the same or intuitable but many pitfalls remain. Interpreting the original text required not just competent French-English translating but also a good understanding of the terminology of geology and vertebrate anatomy. The translator, Chris Spence, is described as an "amateur paleontologist" but he makes several mistakes beyond those that would be considered just "awkward English." An example of "awkward English" is his phrase "at the limit between two Devonian stages..." on page 63. He uses "limit" because it is so close to the appropriate French word "limite." But in English, you would say "at the boundary between two Devonian stages" because "boundary" is the word commonly used to express a border between geologic time units (as in "K-T boundary"). It is a fine point that can get past a translator but it should have been picked up by an editor at Indiana University Press. One of Spence's more conspicuous errors is seen on page 28 where he refers to tetrapods discovered in the 20th century as "mentors" to more recently-described forms. I think he meant a word in opposition to "newcomers" but I could not figure out how he came up with "mentors" (no obvious French connection). For the last word on page 69, he employs a false cognate of the French word "bassin" and writes "basin" where he should have said "pelvis," resulting in a baffling sentence. Other problems closer to mere typos include: his choice of "paleosoils" on page 66 when he should have gone with "paleosols"; "chiropters" on page 138 instead of "chiropterans" and "amphisbaenas" on page 156 over "amphisbaenids." On the whole I would have to say that Spence delivered a smooth text. It is a lot more difficult and time-consuming to preserve the meaning of every phrase, sentence, and paragraph of a book in one language and express it fluently in another language than it is for a reviewer to spot isolated problems. Again, a round of editing should have caught at least most of the loose ends. Supporting the text are numerous excellent, and at times imaginative, illustrations by Alain Beneteau. Many of the animals are not quickly recognizable as subjects in American paleo-books so Beneteau's drawings and paintings also offer a variety of fresh faces and forms. Nearly every page facing a solid page of text bears at least one informative chart, artwork, or photograph (SEM photos, close-ups of fossils, shots of scientists in the field, etc.), with some pages carrying several illustrations. I was told about this book by a paleontologist who thinks the pictures alone were worth the purchase price. Looking past the relatively minor negatives, I recommend "Earth Before the Dinosaurs" to fossil collectors of all levels of experience. It is a good introductory book on the early evolution of tetrapods, a subject getting more attention these days. Jess