Robo Alive Dino Fossil Find Series 1

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One feature found in shells of the modern Nautilus is the variation in the shape and size of the shell according to the sex of the animal, the shell of the male being slightly smaller and wider than that of the female. This sexual dimorphism is thought to be an explanation for the variation in size of certain ammonite shells of the same species, the larger shell (the macroconch) being female, and the smaller shell (the microconch) being male. This is thought to be because the female required a larger body size for egg production. A good example of this sexual variation is found in Bifericeras from the early part of the Jurassic period of Europe. Gittenberger, E. (1991). "What about non-adaptive radiation?". Biological Journal of the Linnean Society. 43 (4): 263–272. doi: 10.1111/j.1095-8312.1991.tb00598.x. The Greenland shark, a big deep-ocean predator, can claim the distinction of being Earth's longest-living vertebrate, with a lifespan reaching roughly 400 years.

Fordyce, R.E.; Marx, F.G. (2013). "The pygmy right whale Caperea marginata: The last of the cetotheres". Proceedings of the Royal SocietyB: Biological Sciences. 280 (1753): 1–6. doi: 10.1098/rspb.2012.2645. PMC 3574355. PMID 23256199. By studying human fossils and ancient Australian cave paintings that were dated to the same time period, paleontologists hypothesized that human beings—the earliest people to inhabit Australia—may have contributed to the extinction of Genyornis. Estes, Suzanne; Arnold, Stevan (2007). "Resolving the paradox of stasis: Models with stabilizing selection explain evolutionary divergence on all timescales". The American Naturalist. 169 (2): 227–244. doi: 10.1086/510633. PMID 17211806. S2CID 18734233. The lateral region involves the first saddle and lobe pair past the external region as the suture line extends up the side of the shell. The lateral saddle and lobe are usually larger than the ventral saddle and lobe. Additional lobes developing towards the inner edge of a whorl are labelled umbilical lobes, which increase in number through ammonoid evolution as well as an individual ammonoid's development. In many cases the distinction between the lateral and umbilical regions are unclear; new umbilical features can develop from subdivisions of other umbilical features, or from subdivisions of lateral features. Lobes and saddles which are so far towards the center of the whorl that they are covered up by succeeding whorls are labelled internal (or dorsal) lobes and saddles. Planorbicone – Intermediate between serpenticones and spherocones: Moderately broad, evolute to involute. Wider and more involute ammonoids on the serpenticone-spherocone spectrum are termed Cadicones.Klug, Christian; Kröger, Björn; Vinther, Jakob; Fuchs, Dirk (August 2015). "Ancestry, Origin and Early Evolution of Ammonoids". In Christian Klug; Dieter Korn; Kenneth De Baets; Isabelle Kruta; Royal H. Mapes (eds.). Ammonoid Paleobiology: From macroevolution to paleogeography. Topics in Geobiology 44. Vol.44. Springer. pp.3–24. doi: 10.1007/978-94-017-9633-0_1. ISBN 978-94-017-9632-3. Sexual dimorphism [ edit ] Discoscaphites iris, Owl Creek Formation (Upper Cretaceous), Ripley, Mississippi, US Before the body disappears completely, it is buried by sediment - usually mud, sand or silt. Often at this point only the bones and teeth remain. In contrast to index fossils, living fossils are organisms that have existed for a tremendously long period of time without changing very much at all. For example, the Lingulata brachiopods have existed from the Cambrian period to the present, a time span of over 500 million years! Modern specimens of Lingulata are almost indistinguishable from their fossil counterparts (Figure 11.8).

Pelicans ( Pelecanus) – form has been virtually unchanged since the Eocene, and is noted to have been even more conserved across the Cenozoic than that of crocodiles. [48] They show little morphological divergence, whether from early members of the lineage, or among extant species.

Sea urchins

A living fossil is an extant taxon that cosmetically resembles related species known only from the fossil record. To be considered a living fossil, the fossil species must be old relative to the time of origin of the extant clade. Living fossils commonly are of species-poor lineages, but they need not be. While the body plan of a living fossil remains superficially similar, it is never the same species as the remote relatives it resembles, because genetic drift would inevitably change its chromosomal structure. Other sensory organs possessed by trilobites included pits, canals, tubercles and spines on the surface of the exoskeleton. Soft parts