Abstract
BackgroundLong bone histology of the most derived Sauropoda, the Titanosauria suggests that titanosaurian long bone histology differs from the uniform bone histology of basal Sauropoda. Here we describe the long bone histology of the titanosaur Ampelosaurus atacis and compare it to that of basal neosauropods and other titanosaurs to clarify if a special titanosaur bone histology exists.Methodology/Principal Findings Ampelosaurus retains the laminar vascular organization of basal Sauropoda, but throughout most of cortical growth, the scaffolding of the fibrolamellar bone, which usually is laid down as matrix of woven bone, is laid down as parallel-fibered or lamellar bone matrix instead. The remodeling process by secondary osteons is very extensive and overruns the periosteal bone deposition before skeletal maturity is reached. Thus, no EFS is identifiable. Compared to the atypical bone histology of Ampelosaurus, the large titanosaur Alamosaurus shows typical laminar fibrolamellar bone. The titanosaurs Phuwiangosaurus, Lirainosaurus, and Magyarosaurus, although differing in certain features, all show this same low amount or absence of woven bone from the scaffolding of the fibrolamellar bone, indicating a clear reduction in growth rate resulting in a higher bone tissue organization. To describe the peculiar primary cortical bone tissue of Phuwiangosaurus, Ampelosaurus, Lirainosaurus, and Magyarosaurus, we here introduce a new term, “modified laminar bone” (MLB).Conclusions/SignificanceImportantly, MLB is as yet not known from extant animals. At least in Lirainosaurus and Magyarosaurus the reduction of growth rate indicated by MLB is coupled with a drastic body size reduction and maybe also a reduction in metabolic rate, interpreted as a result of dwarfing on the European islands during the Late Cretaceous. Phuwiangosaurus and Ampelosaurus both show a similar reduction in growth rate but not in body size, possibly indicating also a reduced metabolic rate. The large titanosaur Alamosaurus, on the other hand, retained the plesiomorphic bone histology of basal neosauropods.
Highlights
Long Bone Histology of Sauropoda The histology of fossil tetrapod bones has proven to be a rich source of paleobiological and evolutionary information [1,2,3,4], for groups that have no living relatives or in which the living relatives occupy a fundamentally different ecological niche
Taxon sampling is limited (Alamosaurus, Ampelosaurus, Lirainosaurus, Magyarosaurus, Phuwiangosaurus), four out of the five taxa (Alamosaurus being the exception) show a peculiar primary cortical tissue, here termed Modified Laminar Bone (MLB), that evolved from the standard laminar fibrolamellar bone (FLB) of sauropods
During the evolution of modified laminar bone’’ (MLB), the laminar organization of the vascular network was retained, but only the initial scaffolding of bone deposition in early ontogenetic stages contains a low amount of woven bone matrix
Summary
Long Bone Histology of Sauropoda The histology of fossil tetrapod bones has proven to be a rich source of paleobiological and evolutionary information [1,2,3,4], for groups that have no living relatives or in which the living relatives occupy a fundamentally different ecological niche. Evidence has accumulated [11,12,13] that titanosaurian long bone histology may be different from that of the more basal neosauropods, i.e., diplodocoid and basal macronarian sauropods of the Jurassic While some of these differences may be attributed to evolutionary size changes related to island habitats (Magyarosaurus [13]; Lirainosaurus [12]), the case is less clear-cut in the limited number of other taxa (Phuwiangosaurus [11]) that have been studied. Contrary to those smaller sized forms, the large titanosaur Alamosaurus shows a more typical bone tissue type comparable to that of the Jurassic sauropods [7]. We describe the long bone histology of the titanosaur Ampelosaurus atacis and compare it to that of basal neosauropods and other titanosaurs to clarify if a special titanosaur bone histology exists
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
