Dino pisze:nazuul pisze:Utahraptor pisze:nazuul pisze:Sarmientosaurus i Notocolossus (dwa ostatnie z powodów nieujawnionych w ED)
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Martínez, R.D.F., Lamanna, M.C., Novas, F.E., Ridgely, R.C., Casal, G.A., Martínez, J.E, Vita, J.R. & Witmer, L.M. (2016) A Basal Lithostrotian Titanosaur (Dinosauria: Sauropoda) with a Complete Skull: Implications for the Evolution and Paleobiology of Titanosauria. PLoS ONE 11(4): e0151661. doi:10.1371/journal.pone.0151661 pisze:Our cladistic analyses have consistently recovered Sarmientosaurus as an archaic lithostrotian titanosaur, phylogenetically basal to taxa such as Nemegtosaurus, Rapetosaurus, and Tapuiasaurus. The phylogenetic position of the new Patagonian form relative to Tapuiasaurus is of particular interest given the respective geologic ages of these sauropods. Tapuiasaurus comes from Aptian (possibly early Aptian) strata in Brazil [14], whereas Sarmientosaurus is from Cenomanian—Turonian beds in southern Argentina. According to the current Geologic Time Scale [65], the Aptian extends from 126–113 Ma and the Cenomanian—Turonian from 100–89.8 Ma. Consequently, the comparatively derived Brazilian form is at least 13 million years—and more probably some 25 million years—older than the new Argentinean titanosaur.
The craniodental anatomies of these sauropods differ dramatically. Sarmientosaurus retains a relatively plesiomorphic skull and wide-crowned dentition reminiscent of those of non-titanosaurian titanosauriforms such as Abydosaurus and Giraffatitan. Tapuiasaurus, by contrast, closely resembles other derived titanosaurians in having a proportionally low and elongate skull with narrow-crowned teeth restricted to the rostral ends of the jaws. The occurrence of Sarmientosaurus in the Cenomanian—Turonian suggests that, in South America and perhaps elsewhere, comparatively short-skulled, broad-toothed titanosaurs persisted alongside their more advanced, diplodocoid-like relatives for tens of millions of years, at least into the early stages of the Late Cretaceous. The disparate skull and tooth morphologies of these titanosaurs may well reflect distinct dietary preferences and/or feeding mechanisms; if so, the coexistence of these animals may have been facilitated by niche partitioning.
Another notable aspect of our strict consensus trees is that, in contrast to several earlier studies [12,14,180], Rapetosaurus and Tapuiasaurus are never recovered as members of Nemegtosauridae. Nemegtosauridae is defined as the stem-based clade that includes all titanosaurs more closely related to Nemegtosaurus than to Saltasaurus; apart from the former genus, the only other indisputable nemegtosaurid is Quaesitosaurus [11]. Intriguingly, until now, Nemegtosaurus, Rapetosaurus, and Tapuiasaurus were the only titanosaurians for which complete or nearly complete skulls had been described. We therefore suspect that the purported monophyly of these three genera has been an artifact of differential preservation among titanosaur taxa. Stated simply, Nemegtosaurus, Rapetosaurus, and Tapuiasaurus have been artificially ‘pulled’ together in previous analyses because they were the only titanosaurs for which most craniomandibular characters could be definitively scored. (D’Emic [115]:644–646] briefly discussed this phenomenon as it pertains to the phylogeny of Titanosauriformes more broadly, terming it the “monophyly of the preserved.”) The incorporation of Sarmientosaurus into phylogenetic analyses has had the effect of redistributing craniomandibular character data throughout Titanosauria, such that many putative nemegtosaurid synapomorphies are now proposed to characterize wider taxonomic groups. Notably, Wilson ([11]:313) predicted such an eventuality: “As more well-preserved titanosaur skulls are discovered, the distribution of characters supporting nemegtosaurid monophyly will likely broaden to diagnose more inclusive groups.”
Lastly, an unexpected result of our phylogenetic analyses involves the Early Cretaceous North American titanosauriform Abydosaurus [98]. This taxon has been nested within Brachiosauridae in all previous analyses in which it has been included [98,115,124,159,191]. In our strict consensus trees, however, Abydosaurus is always recovered as a basal titanosauriform that is closer to Titanosauria than to the only uncontroversial brachiosaurid in our matrices, Giraffatitan. This suggests that Abydosaurus may not be a member of Brachiosauridae, and that this clade (at least as it has been conceived by some recent authors [98,115,124]) may be paraphyletic. Intriguingly, Abydosaurus exhibits similarities with Sarmientosaurus: for instance, the orbit is proportionally large and the tooth count is closely comparable in both taxa. Most notably, Abydosaurus and Sarmientosaurus share a foramen on the lateral surface of the postorbital, near the junction of the rostrodorsal, caudodorsal, and ventral processes, a condition that is presently unique to these genera, but that may also occur in other sauropods (L.M.W., unpublished data). The significance of these morphologies should be investigated in future phylogenetic analyses of Titanosauriformes. Also, the comprehensive description of the Abydosaurus material (especially the abundant postcranial remains [98]) will undoubtedly clarify the systematic position of this taxon.
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The premaxillary and maxillary teeth of Sarmientosaurus exhibit lingual and distal wear facets accompanied by slight, submesially-placed grooves. The functional dentary teeth do not have labial wear facets, but instead have strong distal wear facets. These distal wear facets on the dentary teeth are not present in the sample of 185 titanosaurian teeth from a diversity of geological formations analyzed by García and Cerda [61].
Calvo [140,145] considered the teeth of the sauropod ‘Asiatosaurus mongoliensis’ (widely regarded as a nomen dubium; [90,203,204]) to belong to Titanosauriformes due to the high angle of their wear. Nevertheless, the two teeth of this taxon described by Osborn [146] have mesiodistal wear facets that imply interdigitated occlusion as in Camarasaurus [150]. Calvo [140,145] regarded the jaw movements of ‘Asiatosaurus’ to be orthal, as in titanosauriforms. In Sarmientosaurus, the prominent distal wear facet of the dentary teeth—which is oriented parallel to the long axis of the tooth—is correlated with the submesial groove of the upper teeth. This demonstrates the existence of some degree of occlusal interdigitation, as present in the aforementioned macronarians but absent in advanced titanosaurians. Based on the subvertical wear facets of its teeth and the general orientation of its dental microwear [113], the new Patagonian taxon would have employed orthal jaw movements.
The peculiar orientation of the tooth crowns of Sarmientosaurus is not observed in other sauropods, and its functional significance is therefore difficult to interpret. However, the combination of subvertical premaxillary and mesial maxillary crowns and recumbent dentary crowns might indicate the existence of specialized shearing movements in the rostral part of the mouth that would have facilitated the slicing of plant matter.
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We examined the pneumaticity of the preserved vertebrae of Sarmientosaurus via a CT-based analysis, using the methodology proposed by Wedel [226]. To our knowledge, this analysis is the first of its kind yet performed on a titanosaurian cervical series. CT images revealed extraordinarily high ASP values—up to 88.19% air—in each axial cross section (see Table 6). The average ASP of the Sarmientosaurus axis and third cervical vertebra is 81.64%, whereas that of the sixth cervical vertebra is 70.56% and the seventh is 75.18%. Lower ASP values are generally observed in the articular condyles and cotyles of the centra; this is probably a consequence of biomechanical factors related to maintaining structural strength. By contrast, a cervical vertebra of a juvenile individual of the non-titanosaurian somphospondylan or basal titanosaurian Phuwiangosaurus has a mid-centrum ASP of only 55% [165,226]. Although ASPs vary considerably in non-titanosaurian sauropods, the maximum recorded values for cervical centra are 74% at mid-centrum in the titanosauriform Sauroposeidon and 77% near the caudal cotyle in the diplodocid Tornieria ([219]:table 7.2). Sereno et al. [123] reported extreme cervical vertebral pneumaticity—probably even greater than that of Sarmientosaurus—in the African rebbachisaurid Nigersaurus, but did not calculate an ASP or comparable quantitative value. Nevertheless, it is clear that the new Patagonian titanosaur possesses some of the most extensively pneumatized cervical centra yet documented within Sauropoda.
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When considering the paleobiological significance of the highly pneumatic cervical vertebrae of Sarmientosaurus, we should also take into account the other distinctive morphologies of the taxon, such as exceptionally elongate cervical vertebrae accompanied by ossified, ventrolaterally-positioned tendons, a downwardly-angled skull, and a habitually neutral or proportionally low neck posture. This suite of features would have made the new titanosaur an efficient harvester of vegetation, probably from plants growing at medium to low heights. Interestingly, Nigersaurus also possesses the combination of an exceptionally pneumatized neck and a downward-facing snout [123]; nevertheless, the two forms differ considerably in that Sarmientosaurus has a much more robustly-constructed skull and teeth and (probably) a proportionally longer neck. These shared cranial and cervical features of Nigersaurus and Sarmientosaurus represent a series of previously undocumented convergences between Diplodocoidea and Titanosauria. Perhaps not coincidentally, these two sauropod genera inhabited mid-Cretaceous paleoecosystems in the western Gondwanan continents (Afro-Arabia and South America, respectively). This raises the intriguing possibility that the convergent morphologies observed in these taxa may represent an adaptive response to some factor common to these paleoenvironments, perhaps the diversification and increasing dominance of angiosperms during the mid-Cretaceous.
Conclusions
Sarmientosaurus musacchioi is the first titanosaurian sauropod from southern South America for which an articulated, virtually complete adult skull has been discovered. Phylogenetic analyses demonstrate that the new taxon is an archaic member of the titanosaurian subclade Lithostrotia, occupying a position more derived than Malawisaurus but more basal than taxa frequently regarded as nemegtosaurids (Nemegtosaurus, Rapetosaurus, and Tapuiasaurus) and saltasaurid titanosaurs such as Alamosaurus, Neuquensaurus, and Saltasaurus. As such, Sarmientosaurus is the most basal known titanosaur to be represented by a well-preserved skull. The new taxon exhibits a previously-undocumented cranial form that consists of an amalgam of plesiomorphic titanosauriform features such as a comparatively broad snout with a large narial fossa and a deep mandibular adductor chamber with more derived morphologies such as an elongate rostral process of the prefrontal (Figs 33 and 34).
(...) Sarmientosaurus possesses a number of distinctive features that have not been observed in other sauropods. The cranial endocast presents among the most complete information about the brain and sensory systems for any sauropod, let alone titanosaurs, and thus will be important for the developing picture of neural evolution in Sauropoda. The endocast and inner ear possess clear titanosaurian apomorphies, but also retain a number of plesiomorphies, supporting the hypothesized phylogenetic position of Sarmientosaurus as a basal member of Lithostrotia.
González Riga, B.J., Lamanna, M.C., Ortiz David, L.D., Calvo, J.O. & Coria, J.P. (2016) A gigantic new dinosaur from Argentina and the evolution of the sauropod hind foot. Scientific Reports 6: 19165. doi:10.1038/srep19165 pisze:Therefore, assuming that the referred specimen UNCUYO-LD 302 pertains to this taxon, Notocolossus is significant in being the largest titanosaur—and possibly the most massive terrestrial animal—for which the pedal skeleton is completely represented.
The pes of Notocolossus exhibits several characters that are unique within Titanosauria, or, in some cases, Sauropoda as a whole. It has short, thick metatarsals, all of which are approximately the same length (Table 2; Supplementary Table S3); among these, the relative length and robusticity of metatarsals I and V is remarkable. This morphology results in a pes that is comparatively shorter and more mediolaterally symmetrical than those of other titanosaurs, and indeed, most other sauropods – a foot in which the weight of the animal appears to have been more evenly distributed through the metatarsus. The Notocolossus pes differs considerably from those of other neosauropods, in which metatarsals I–IV exhibit a significant increase in length and a concomitant decrease in robusticity. In these taxa, metatarsal IV is generally 40–50 percent longer than metatarsal I; furthermore, the proximal phalanges are often proportionally less robust than are those of Notocolossus. In these neosauropods, the hind foot is strongly entaxonic (i.e., more robustly constructed medially than laterally), and weight was presumably borne primarily by the first three digits. Given the enormous size of Notocolossus, its distinctive, relatively homogeneous pedal morphology may constitute an adaptation for supporting a greatly elevated body mass. The fact that the only other sauropod specimen with a comparably robust and elongate metatarsal V is the even larger titanosaurian pes NMMNH P-49967 (?Alamosaurus) is consistent with this interpretation (although the metatarsus of that specimen differs in other respects from that of Notocolossus).
(...) the new taxon indicates that titanosaurian morphological diversity was even greater than previously appreciated, and that members of this group exhibited at least two principal pedal morphotypes: (1) comparatively short, robust, and mediolaterally symmetrical (as in Notocolossus), and (2) elongate and strongly entaxonic (e.g., A. wichmannianus, Bonitasaura, Epachthosaurus, Rapetosaurus, ?Alamosaurus, the Agua del Padrillo and La Invernada titanosaurs).
(...) Among sauropods, the pedal unguals of Notocolossus are unique in being unusually short and distally truncated. Although, as mentioned above, it is possible that their peculiar appearance is pathological—pathologies have been documented in sauropod pedes before33,34—we consider this less likely because all three unguals exhibit similar morphologies and there is no evidence of pathology in the other pedal elements.
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Utahraptor pisze:nazuul pisze:Podsumowanie warto na główną wrzucić.
Popieram. Bardzo fajne zestawienie.
Miałem na myśli tekst Ag.Enta, a widzę, że wrzucono też moją odpowiedź na pytania Utahraptora wyrwaną z kontekstu:
http://www.dinozaury.com/2017/01/03/pod ... -kregowcow
Proszę ją usunąć albo właściwie uzupełnić (to pierwsze jest bardziej sensowne, bo jest to mało wartościowa wypowiedź).
Uzupełnić o co? Jak bardzo brak początku (z, moim zdaniem oksymoronem/błędem frazeologicznym "moim obiektywnym okiem") ugruntowuje kontekst wypowiedzi? Zgodnie z życzeniem, cytacja zostanie usunięta.
To:
nazuul pisze:W liście dino2016
Otóż usuwając ww. kontekst, wychodzi, że - skoro zagajenie brzmi "poniżej redaktorzy Dinozaury.com na łamach naszego forum dyskusyjnego wybierają najciekawsze odkrycia paleontologiczne w zeszłym roku." - za najciekawsze odkrycia paleontologiczne w zeszłym roku uważam wymienione przeze mnie dinozaury, podczas gdy za najważniejsze odkrycia paleontologiczne w zeszłym roku nie uważam żadnych dinozaurów.
Utahraptor zadał dwa pytania, na oba odpowiedziałem jak umiałem. Z całego multum interesujących spraw podałem ozimka, ale prosciej było odpowiedzieć na pierwsze pytanie, gdzie zadający podał listę do wyboru.
Dino pisze:nazuul pisze:
Co do podsumowania na głównej:
Używanie znaku (C) co najmniej w odniesieniu do niektórych grafik jest błędem.
Niewykluczone, że gdyby wskazano o jakie "niektóre grafiki" chodzi, może zostałoby to zmienione.
Myślałem, że to oczywiste.
W grafikach dostępnych na licencjach typu Creative Commons itp. (czyli co najmniej Gualicho, Ozimek, Buriolestes, Limusaurus - podaję, bo kojarzę, że na nich są, pozostałych nie sprawdzałem) należałoby wskazać licencję i podać jej linka.