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527 results for “Mesozoic.”
Data from: Buoyancy mechanisms limit preservation of coleoid cephalopod soft tissues in Mesozoic Lagerstätten
Coleoid cephalopods are characterized by internalization of their shell, and are divided into the ten-armed Decabrachia (squids and cuttlefish) and the eight-armed Vampyropoda (octopuses and vampire squid). They have a rich fossil record predominantly of the limited biomineralized skeletal elements they possess: arm hooks, statoliths, mouthparts (the buccal mass) and internal shell (gladius or pen), although exquisitely preserved soft tissue coleoids are known from several Lagerstätten worldwide. Recent studies have shown that although morphological similarities between extant decabrachian gladii and fossil examples exist, no known examples of fossil decabrachians are currently known. However, molecular clock data and phylogenetic bracketing suggest that they should be present in Lagerstätten that are rich in vampyropod soft tissue fossils (i.e. Hâkel and Hâdjoula Lagerstätten, Cretaceous, Lebanon). We propose that a hitherto unknown taphonomic bias pertaining to the differing methods of buoyancy control within coleoid groups limits preservation potential. Both negatively and neutrally buoyant decabrachians use chemical buoyancy control (ammonia) whereas vampyropods do not. In the event of rapid burial in an environment conducive to exceptional preservation, ammonia dramatically decreases the ability of the decabrachian carcass to generate the required pH for authigenic calcium phosphate replacement, limiting its preservation potential. Moreover, the greater surface area and comparatively fragile dermis further decrease the potential for fossilization. This taphonomic bias may have contributed to the lack of preserved labile soft-tissues in other cephalopods groups such as the ammonoids.
Data from: The Muensterelloidea: phylogeny and character evolution of Mesozoic stem octopods
The Muensterelloidea is a superfamily of teudopseid octobrachians with a posteriorly patella-shaped gladius. A morphometric comparison based on 148 muensterelloid gladii has yielded five new species accommodated in three new genera: Engeseriteuthis arcuatus gen. nov. sp. nov., Muensterella jillae sp. nov., Muensterella spinosa sp. nov., Tyrionella fauseri gen. nov. sp. nov., and Muensterellina johnjagti gen. nov. sp. nov. Cretaceous taxa "Tusoteuthis" cobbani and "Muensterella" tonii are re-combined and placed within the genus Enchoteuthis. We introduce categories for gladius proportions applicable for both muensterelloid and non-muensterelloid octobrachian gladii. 2D-landmark analyses including 64 muensterelloid and non-muensterelloid gladii statistically confirms that the Muensterelloidea possess the smallest median field sizes of all Mesozoic gladii. The lateral field-dominated "gladius" of the family Patelloctopodidae (Patelloctopus, Pearceiteuthis) is considered to be vestigial; i.e. shorter than the mantle length; a view that expose the Patelloctopodidae as the last shared ancestors of incirrate and cirrate octopods. According to a phylogenetic analysis based on 31 gladius characters, the Muensterelloidea mainly consists of the "Muensterella-Enchoteuthidae" and the "patelloctopodid" clade. Ancestral character state reconstructions suggest that an increasing posterior growth front is accompanied by a continuous decrease of the median field length. This milestone in the evolution of the octopod gladius vestige occurred between the Early and Middle Jurassic. The benthic life style of incirrate octopods (including Cretaceous palaeoctopodids) has been adopted from Jurassic Patelloctopodidae, which itself arose from nectonic to nectobenthic teudopseid ancestors. There is currently no evidence to assume a pelagic origin for benthic octopods.
Data from: Bayesian tip dating reveals heterogeneous morphological clocks in Mesozoic birds
Recently, comprehensive morphological datasets including nearly all the well-recognized Mesozoic birds became available, making it feasible for statistically rigorous methods to unveil finer evolutionary patterns during early avian evolution. Here, we exploited the advantage of Bayesian tip dating under relaxed morphological clocks to estimate both the divergence times and evolutionary rates while accounting for their uncertainties. We further subdivided the characters into six body regions (i.e., skull, axial skeleton, pectoral girdle and sternum, forelimb, pelvic girdle, and hindlimb) to assess evolutionary rate heterogeneity both along the lineages and across partitions. We observed extremely high rates of morphological character changes during early avian evolution and the clock rates are quite heterogeneous among the six regions. The branch subtending Pygostylia shows extremely high rate in the axial skeleton, while the branches subtending Ornithothoraces and Enantiornithes show notably high rates in the pectoral girdle and sternum, and moderately high rates in the forelimb. The extensive modifications in these body regions largely correspond to refinement of the flight capability. This study reveals the power and flexibility of Bayesian tip dating implemented in MrBayes to investigate evolutionary dynamics in deep time.
Data from: A new global palaeobiogeographical model for the late Mesozoic and early Tertiary
Late Mesozoic palaeobiogeography has been characterized by a distinction between the northern territories of Laurasia and the southern landmasses of Gondwana. The repeated discovery of Gondwanan lineages in Laurasia has led to the proposal of alternative scenarios to explain these anomalous occurrences. A new biogeographical model for late Mesozoic terrestrial ecosystems is here proposed, in which Europe and 'Gondwanan' territories possessed a common Eurogondwanan fauna during the earliest Cretaceous. Subsequently, following the Hauterivian, Europe severed from Africa and connected to Asiamerica resulting in a faunal interchange. This model explains the presence of 'Gondwanan' taxa in Laurasia and the absence of Laurasian forms in the southern territories during the Cretaceous. In order to test this new palaeobiogeographical model, tree reconciliation analyses (TRAs) were performed based on biogeographical signals provided by a supertree of late Mesozoic archosaurs. The TRAs found significant evidence for the presence of an earliest Cretaceous Eurogondwanan fauna, followed by a relatively short-term Gondwana-Laurasia dichotomy. The analysis recovered evidence for a biogeographical re-connection of the European territories with Africa and South America-Antarctica during the Campanian to Maastrichtian time-slice. This biogeographical scenario appears to continue through the early Tertiary and sheds light on the trans-Atlantic disjunct distributions of several extant plant and animal groups.
Data from: ENIGMATIC HOOK-LIKE STRUCTURES IN MESOZOIC AMMONITES (SCAPHITIDAE)
In the last few decades, hook-like structures have been reported in the Mesozoic ammonite family Scaphitidae. Despite their exceptional preservation and debates about their function, no detailed reconstruction of them has yet been made. For the first time, we describe the composition and detailed morphology of these structures in the body chambers of six specimens of the Campanian ammonite Rhaeboceras halli (Meek and Hayden) using high resolution X-ray imaging. The hook-like structures are composed of a thin layer of brushite. The base of the hooks is open on one side forming an internal cavity, now filled with sediments. The tips of the hooks end in one or two cusps or, rarely, none at all. We used geometric morphometrics to capture the morphological disparity of the bicuspidate morphotypes comprising 98% of the hooks. Principal component analysis revealed chirality among the hooks and a cluster analysis (Gaussian mixture) recognized five main morphologies. Contrary to previous interpretation of these structures, we conclude that they are not radular teeth. They are much larger and more variable in size and shape than any known ammonite radulae and completely out of proportion with respect to the size of the jaw. The chirality, the hook-like shape, and the absence of a size relationship between the hooks and the body chambers in which they occur, lead us to propose that these hooks could represent elements of the brachial crown related to copulatory behavior. If so, these would be the first reported remnants of brachial crowns in ammonites.
FIGURE 13 in Venation pattern and revision of Orthoptera sensu nov. and sister groups. Phylogeny of Palaeozoic and Mesozoic Orthoptera sensu nov.
FIGURE 13. Gerarus bruesi, holotype specimen MNHNLPR.51164 (counterpart): reconstruction
The Mesozoic terminated in boreal spring
<p><strong>The Cretaceous-Paleogene (K-Pg) mass extinction ~66 million years ago (Ma) was triggered by the Chicxulub impact on the present-day Yucatán Peninsula. This event caused the highly selective extinction that eliminated ~76% of species, including all non-avian dinosaurs, pterosaurs, ammonites, rudists and most marine reptiles. The timing of the impact and its aftermath have mainly been studied on millennial timescales, leaving the season of the impact unconstrained. By studying fishes that died on the day the Mesozoic ended, we here demonstrate that the impact that caused the K-Pg mass extinction took place during boreal spring. Osteohistology together with stable isotope records of exceptionally preserved perichondral and dermal bones in acipenseriform fishes from the Tanis impact-induced seiche deposits reveal annual cyclicity across the final years of the Cretaceous. Annual life cycles, involving seasonal timing and duration of reproduction, feeding, hibernation, and aestivation, vary strongly across latest Cretaceous biotic clades. We postulate that the timing of the Chicxulub impact in boreal spring and austral autumn significantly influenced selective biotic survival across the K-Pg boundary.</strong></p> <p>All tomographic data (5 stacks of 6 specimens in total) are available here. The methods through which they were acquired:</p> <p><strong>Propagation Phase Contrast Synchrotron Radiation Micro Computed Tomography</strong> </p> <p>Paddlefish specimen FAU.DGS.ND.161.4559.T lacks the paddle-shaped rostrum and all aspects caudal to the pectoral girdle. FAU.DGS.ND.161.4559.T was provided by the Palm Beach Museum of Natural History. Data acquisition took place in May 2018 on Beamline BM05 at the European Synchrotron Radiation Facility, Grenoble, France. The complete specimen was scanned at an average energy of 132 keV using the white beam of BM05 filtered with 0.4 mm of Mo and 9 mm of Cu. The detector was composed of a 2-mm-thick LuAG:Ce scintillator optically coupled to a PCO edge 4.2 CLHS sCMOS camera. The resulting voxel size was 43.5 µm. In order to obtain sufficient propagation phase contrast, the distance between the sample and the detector was set at 5 m. A total of 205 scans, each consisting of 5000 projections taken at 7 ms intervals, were performed with a vertical displacement of 1.4 mm at a vertical field of view of 2.8 mm to ensure a double scan of the complete samples. Scans were performed in half-acquisition mode to enlarge the lateral field of view. The volume was reconstructed using single-distance phase retrieval algorithm coupled with filtered back projection as implemented in the ESRF software PyHST2. Vertical concatenation, 16-bit conversion, and ring artefact corrections were performed using MATLAB scripts developed in-house. The gill region and impact spherules were subsequently scanned at a voxel size of 13.67 μm (filters: 0.4 mm of Mo and 6 mm of Cu, scintillator: LuAG:Ce, 500 μm thick, detected energy: 166 keV, propagation distance: 2.5 m). The samples were scanned in half-acquisition mode in two columns of 77 scans, each consisting of 4998 projections with exposure times of 0.05 s, that were laterally concatenated after reconstruction. Finally, samples (VUA.GG.2017.X-2724) from the paddlefish dentaries and (VUA.GG.2017.MDX-3, VUA.GG.2017.X-2743M and VUA.GG.2017.X-2744M) sturgeon pectoral fin spines were scanned at 4.35 µm voxel size for osteohistological analysis (filters: 3.5 mm of Al plus 11 bars Al with a diameter of 5 mm, scintillator: LuAG:Ce scintillator, 500 µm thick, detected energy: 92 keV, propagation distance: 1.5 m). The samples were scanned in half-acquisition mode in one single column of 22 scans, each consisting of 4998 projections with exposure times of 60 ms.</p> <p> </p> <p>For more information please see paleo.esrf.eu</p> <p>Please cite the original article:https://www.nature.com/articles/s41586-022-04446-1</p>
Functional and ecomorphological evolution of orbit shape in Mesozoic archosaurs is driven by body size and diet: Geometric morphometric data, 3D models (stl files), FEA models (Hypermesh, Abaqus files)
<p class="MsoNormal">The orbit is one of several skull openings in the archosauromorph skull. Intuitively, it could be assumed that orbit shape would closely approximate the shape and size of the eyeball resulting in a predominantly circular morphology. However, a quantification of orbit shape across Archosauromorpha using a geometric morphometric approach demonstrates a large morphological diversity despite the fact that the majority of species retained a circular orbit. This morphological diversity is nearly exclusively driven by large (skull length > 1000 mm) and carnivorous species in all studied archosauromorph groups, but particularly prominently in theropod dinosaurs. While circular orbit shapes are retained in most herbivores and smaller species, as well as in juveniles and early ontogenetic stages, large carnivores adopted elliptical and keyhole-shaped orbits. Biomechanical modeling using finite element analysis reveals that these morphologies are beneficial in mitigating and dissipating feeding-induced stresses without additional reinforcement of the bony structure of the skull.</p>
Plate II. Figure 1 in Notes on Mesozoic vertebrate fossils
Plate II. Figure 1.—Left fore leg of Claosaurus annectens, Marsh; outside view, c, coracoid; h, humerus; r, radius; s, scapula; u, ulna; I. first digit; IV. fourth digit. • Figure 2.—Left hind leg of the same individual; outside view, a, astragalus: c, calcaneum; ƒ femur; ƒ', fibula; il, ilium; is, ischium; p, pubis; p', postpubis; t, tibia. Figures 1 and 2 are one-tweuntieth natural size. Figure 3.—Pelvis of the same individual; seen from the left. One-sixteenth natural size, a, acetabulum; other letters as in figure 2.
Figure 4 from: Woolley C (2016) The first scarabaeid beetle (Coleoptera, Scarabaeidae, Melolonthinae) described from the Mesozoic (Late-Cretaceous) of Africa. African Invertebrates 57(1): 53-66. https://doi.org/10.3897/AfrInvertebr.57.8416
Figure 4 - Ceafornotensis archratiras gen. and sp. n.: (A, B, C) holotype BP/2/18654, characters enlarged. Micrographs of: A right protibia B left mandible C aedeagus. Scale bar: 0.5 mm.
Figure 2 from: Woolley C (2016) The first scarabaeid beetle (Coleoptera, Scarabaeidae, Melolonthinae) described from the Mesozoic (Late-Cretaceous) of Africa. African Invertebrates 57(1): 53-66. https://doi.org/10.3897/AfrInvertebr.57.8416
Figure 2 - Ceafornotensis archratiras gen. and sp. n.: holotype BP/2/18654, habitus. Abbreviations: ae – aedeagus, a.l. – antennal lamellae, b.l. – basal lobe of mandible, cl – clypeus, g.l. – genal lobe, la? – labrum?, ma – mandible, ms – metasternum, msc – mesocoxa, msp – mesopisternum, mtc – metacoxa, mtp – metepisternum, pa – parameres, prc – procoxa, pt. I.? – protarsus I?, te? – tentorium?. Scale bar: 1 mm.
Figure 1 from: Woolley C (2016) The first scarabaeid beetle (Coleoptera, Scarabaeidae, Melolonthinae) described from the Mesozoic (Late-Cretaceous) of Africa. African Invertebrates 57(1): 53-66. https://doi.org/10.3897/AfrInvertebr.57.8416
Figure 1 - Strict consensus of six most parsimonious trees showing characters (above) and state (below). Bootstrap support values are given in parentheses (tree length=275 steps, ensemble consistency index (CI) = 0.39, ensemble retention index (RI) = 0.64). Ceafornotensis archratiras is referred to as "Orapa fossil". Character set from Bai et al. (2011).
Figure 3 from: Woolley C (2016) The first scarabaeid beetle (Coleoptera, Scarabaeidae, Melolonthinae) described from the Mesozoic (Late-Cretaceous) of Africa. African Invertebrates 57(1): 53-66. https://doi.org/10.3897/AfrInvertebr.57.8416
Figure 3 - Ceafornotensis archratiras gen. and sp. n.: holotype BP/2/18654, general appearance. Micrographs taken under: A polarised light B low angle unpolarised light. Scale bar: 1 mm.
FIGURE 5 in Taxonomic notes and new species of Burmomiles and Sanaungulus (Coleoptera, Cantharidae) from northern Myanmar during the late Mesozoic
FIGURE 5 Sanaungulus undecimus sp. nov. (MHBU, No. BU-COL-CAN0016): A. Elytra, dorsal view; B. Habitus, ventral view. Scale bars: 1.0 mm.
FIGURE 3 in Taxonomic notes and new species of Burmomiles and Sanaungulus (Coleoptera, Cantharidae) from northern Myanmar during the late Mesozoic
FIGURE 3 Sanaungulus longicornis sp. nov. (MHBU, No. BU-COL-CAN0014): A. head and pronotum, dorsolateral view; B. pronotum and right antennae, dorsolateral view; C. pronotum and elytra, dorsal view; D. terminal two segments, dorsal view; E. reconstructions of terminal two segments, dorsal view. Scale bars: A–B, D–E: 0.5 mm; C: 1.0 mm.
Data from: A multivariate approach to infer locomotor modes in Mesozoic mammals
Ecomorphological diversity of Mesozoic mammals was presumably constrained by selective pressures imposed by contemporary vertebrates. In accordance, Mesozoic mammals for a long time had been viewed as generalized, terrestrial, small-bodied forms with limited locomotor specializations. Recent discoveries of Mesozoic mammal skeletons with distinctive postcranial morphologies have challenged this hypothesis. However, ecomorphological analyses of these new postcrania have focused on a single taxon, a limited region of the skeleton, or have been largely qualitative. For more comprehensive locomotor inference in Mesozoic mammals, we applied multivariate analyses to a morphometric data set of extant small-bodied mammals. We used 30 osteological indices derived from linear measurements of appendicular skeletons of 107 extant taxa that sample 15 orders and eight locomotor modes. Canonical variate analyses show that extant small-bodied mammals of different locomotor modes have detectable and predictable morphologies. The resulting morphospace occupation reveals a morphofunctional continuum that extends from terrestrial to scansorial, arboreal, and gliding modes, reflecting an increasingly slender postcranial skeleton with longer limb output levers adapted for speed and agility, and extends from terrestrial to semiaquatic/semifossorial and fossorial modes, reflecting an increasingly robust postcranial skeleton with shorter limb output levers adapted for powerful, propulsive strokes. We used this morphometric data set to predict locomotor mode in ten Mesozoic mammals within the Docodonta, Multituberculata, Eutriconodonta, "Symmetrodonta," and Eutheria. Our results indicate that these fossil taxa represent five of eight locomotor modes used to classify extant taxa in this study, in some cases confirming and in other cases differing from prior ecomorphological assessments. Together with previous locomotor inferences of 19 additional taxa, these results show that by the Late Jurassic mammals had diversified into all but the saltatorial and active flight locomotor modes, and that this diversification was greatest in the Eutriconodonta and Multituberculata, although sampling of postcranial skeletons remains uneven across taxa and through time.
FIG. 2 in Peligrotherium tropicalis (Mammalia, Dryolestida) from the early Paleocene of Patagonia, a survival from a Mesozoic Gondwanan radiation
FIG. 2. — Peligrotherium tropicalis Bonaparte, Van Valen & Kramartz, 1993 (MLP 90-II-12-58), maxillary fragment with right M1-M2, and left M1 fragment and M2-M4, occlusal view. Abbreviations: ca, anterior crista; cp, posterior crista; pa, paracone. Scale bar: 5 mm.
FIG. 3 in Peligrotherium tropicalis (Mammalia, Dryolestida) from the early Paleocene of Patagonia, a survival from a Mesozoic Gondwanan radiation
FIG. 3. — Peligrotherium tropicalis Bonaparte, Van Valen & Kramartz, 1993 (MLP 90-II-12-58), roots of right M1-M2, anterointernal view. Scale bar: 5 mm.
Figure 19 in A new Thai Mesozoic lungfish (Sarcopterygii, Dipnoi) with an insight into post-Palaeozoic dipnoan evolution
Figure 19. Histogram for the tree length distribution of all (nearly 654 × 106) possible trees using 12 terminal taxa and Dipterus as outgroup. The strict consensus tree of the 12 taxa is shown in the frame. The shortest tree length is 27 steps and the mean length of all trees is 44.95 steps (SD = 2.84). The skewness statistic, g1, is −0.745, indicating a strong phylogenetic signal of the data.
Figure 16 in A new Thai Mesozoic lungfish (Sarcopterygii, Dipnoi) with an insight into post-Palaeozoic dipnoan evolution
Figure 16. Schematic drawings and photographs showing three stages in the evolutionary trend of the 'hard snout' exemplified by Chirodipterus, Ferganoceratodus martini sp. nov. and Neoceratodus forsteri. The upper drawings show reconstructions of the structure in living fishes, the middle line drawings show the mineralized tissues as found in the fossil record and the lowest are photographs of actual specimens (Chirodipterus from Bemis & Northcutt, 1992: figure 24).
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
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International Brain Laboratory public data
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OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.