STRUCTURAL MECHANICS OF PACHYCEPHALOSAUR CRANIA PERMITTED HEAD-BUTTING BEHAVIOR

Abstract: Pachycephalosaurian dinosaurs have dorsally thickened crania and uniquely shaped frontoparietal domes in some genera, suggested as evidence for head-or flank-butting behavior. Trabeculae thought to have resisted impact compression are present as only one histological zone of some pachycephalosaur domes, and are surrounded superficially or replaced by thick compacta in adults. The capabilities of pachycephalosaurian crania for head-butting are testable by finite element analysis (FEA). FEA of 2-and 3-D dorsal skull shapes of adult Homalocephale and Pachycephalosaurus reveal that the domes could withstand considerable impact force at certain closing speeds, and that stress and strain would dissipate efficiently throughout the dorsal portion of the skull before reaching the brain. Greater vaulting of the dome permitted higher impact forces. An analysis restricted to the frontoparietal dome of a subadult pachycephalosaurine, with material properties corresponding to histological zones, shows higher compressive strain (not less) in the trabecular region. The trabecular zone, if present, would not have rigidly resisted compression but rather have allowed slight elastic compression and rebound. Modeled keratinous coverings of varying depth indicate reductions in force and energy transmission to underlying bone. FEA therefore leaves open the possibility of head-butting in both flat-and dome-headed pachycephalosaurs, especially at low collision speeds.

dome
capability
considerable impact force
brain


First arboreal 'pelycosaurs' (Synapsida: Varanopidae) from the early Permian Chemnitz Fossil Lagerstätte, SE Germany, with a review of varanopid phylogeny

Abstract:
A new fossil amniote from the Fossil Forest of Chemnitz (Sakmarian-Artinskian transition, Germany) is described as Ascendonanus nestleri gen. et sp. nov., based on five articulated skeletons with integumentary preservation. The slender animals exhibit a generalistic, lizard-like morphology. However, their synapsid temporal fenestration, ventrally ridged centra and enlarged iliac blades indicate a pelycosaur-grade affiliation. Using a renewed data set for certain early amniotes with a similar typology found Ascendonanus to be a basal varanopid synapsid. This is the first evidence of a varanopid from Saxony and the third from Central Europe, as well as the smallest varanopid at all. Its greatly elongated trunk, enlarged autopodia and strongly curved unguals, along with taphonomical observations, imply an arboreal lifestyle in a dense forest habitat until the whole ecosystem was buried under volcanic deposits. Ascendonanus greatly increases the knowledge on rare basal varanopids; it also reveals a so far unexpected ecotype of early synapsids. Its integumentary structures present the first detailed and soft tissue skin preservation of any Paleozoic synapsid. Further systematic results suggest a varanodontine position for Mycterosaurus, the monophyly of South African varanopids including Anningia and the distinction of a skeletal aggregation previously assigned to Heleosaurus, now renamed as Microvaranops parentis gen. et sp. nov.
Arboreality • Synapsid phylogeny • Adaptation • Cisuralian • Soft tissue preservation • Volcanic taphonomy Kurzfassung Basierend auf fünf artikulierten Skeletten mit Hauterhaltung wird ein neuer, fossiler Amniot aus dem Versteinerten Wald von Chemnitz (Sakmarium-Artinskium-Grenzbereich, Deutschland) beschrieben als Ascendonanus nestleri gen. et sp. nov. Die schlanken Tiere sind von generalistischer, echsenhafter Gestalt. Demgegenüber zeigen die synapsiden Schläfenfenster, ventral gekantete Zentren und vergrößerte Iliumblätter eine Zugehörigkeit zur Pelycosaurier-Stufe an. Unter Anwendung eines erneuerten Datensatzes für ausgewählte frühe Amnioten ähnlicher Typologie wird Ascendonanus zu basalen Varanopiden gestellt. Damit liegt der erste Nachweis eines Varanopiden aus Sachsen und der dritte aus Mitteleuropa vor, zudem der kleinste Varanopide überhaupt. Sein besonders verlängerter Rumpf, vergrößerte Autopodien und stark gekrümmte Krallen sowie taphonomische Beobachtungen legen eine arboreale Lebensweise inmitten eines dichten Waldhabitats nahe, bis das gesamte Ökosystem von vulkanischen Ablagerungen verschüttet wurde. Ascendonanus erweitert die Kenntnis der seltenen basalen Varanopiden enorm, zumal er einen bei frühen Synapsiden bisher unerwarteten Ökotyp aufdeckt. Die Integumentstrukturen stellen die ersten detaillierten und durch Weichteile erhaltenen Hautfunde aller paläozoischen Synapsiden dar. Weitergehende systematische Ergebnisse deuten an: eine varanodontine Position für Mycterosaurus, die Monophylie

varanopid
integumentary preservation
numerous habitat
tree
other organism


The fish trace fossil Undichna from the Cretaceous of Spain

Abstract: The Early Cretaceous Spanish localities of El Montsec and Las Hoyas have yielded the fish trails Undichna britannicaandUndichna unisulcaichnosp. nov. respectively. The former consists of two intertwined waves, and was probably produced by the elopiform Ichthyemidion vidali . Undichna unisulcais characterized by having only a single sinusoidal wave, and was most probably produced by the pycnodontiforms Eo esodonand/or Macromesodon . Reliable criteria that distinguish this ichnospecies from the putative single-waved undertrails of more complex trails include the presence of hyporeliefs below undisturbed lamination and the preservation of epireliefs with lateral levees. The Spanish occurrences represent the first mention of this ichnogenus in post-Palaeozoic strata, and demonstrate that Undichnais not restricted to the Carboniferous–Permian, as previously thought. The lacustrine depositional setting of the two Cretaceous localities is consistent with the known palaeoenvironmental distribution of this ichnotaxon. The disparity between the stratigraphical record of Undichnaand the broad temporal and palaeoenvironmental distribution of fishes capable of producing similar sinusoidal structures presumably reflects a taphonomic filter. Preservation of Undichna is favoured by: absence or scarcity of infaunal burrowers; presence of a very fine-grained, plastic, semiconsolidated substrate; low-energy bottom conditions; and relatively rapid burial with no associated erosion. Freshwater settings present these taphonomic constraints more frequently than other environments; thus preservation of Undichnais favoured in lakes, alluvial swamps and inner regions of estuaries. SI N C E its diagnosis by Anderson (1976) on the basis of material from the Lower Permian of South Africa, the fish ichnogenusUndichnahas been extensively recorded from strata of Late Palaeozoic age in the United States (Archer and Maples 1984; Rindsberg 1990; Buatois e al. 1997), England (Higgs 1988), the Czech Republic (Turek 1989) and Argentina (Buatois and Ma ́ngano 1993a, 1994a). Accordingly, this ichnotaxon seems to have been restricted to the Late Palaeozoic, and more precisely to the Late Namurian–Early Permian (Buatois and Ma ́ngano 1994 a), apparently forming an exception to the rule that trace fossils are commonly typified by long temporal ranges (cf. Frey 1975). In this paper, the ichnogenus Undichna is described for the first time from Mesozoic beds. This ichnotaxon occurs in three Early Cretaceous Spanish localities, already well-known for their body fossil content: La Pedrera, La Cabru ́a, and Las Hoyas. The occurrence of Undichna at La Pedrera was mentioned, but not described, by Gibert (1994, 1995 a, 1995b). In addition, the ocurrence of a new ichnospecies ofUndichna is documented from Las Hoyas. The purpose of this contribution is to describe formally theUndichnafrom La Pedrera and La Cabru ́a, to diagnose the new ichnospecies from Las Hoyas, to identify the fishes that may have produced these traces, and to discuss stratigraphical, palaeoenvironmental, and taphonomic aspects of the ichnogenus. G E O L O G I C A L S E T T I N G A N D S T R A T I G R A P H Y The fish trace fossils described and discussed herein come from three different Spanish fossil sites of Early Cretaceous age and lacustrine origin: La Pedrera and La Cabru ́a (Serra del Montsec, south-central Pyrenees, province of Lleida) and Las Hoyas (Serranı ́a de Cuenca, Iberian Range, province of Cuenca) (Text-fig. 1A). [Palaeontology, Vol. 42, Part 3, 1999, pp. 409–427, 1 pl.] q The Palaeontological Association 410 P A L A E O N T O L O G Y , V O L U M E 4 2


Expansion for the Brachylophosaurus canadensis Collagen I Sequence and Additional Evidence of the Preservation of Cretaceous Protein.

Abstract: Sequence data from biomolecules such as DNA and proteins, which provide critical information for evolutionary studies, have been assumed to be forever outside the reach of dinosaur paleontology. Proteins, which are predicted to have greater longevity than DNA, have been recovered from two nonavian dinosaurs, but these results remain controversial. For proteomic data derived from extinct Mesozoic organisms to reach their greatest potential for investigating questions of phylogeny and paleobiology, it must be shown that peptide sequences can be reliably and reproducibly obtained from fossils and that fragmentary sequences for ancient proteins can be increasingly expanded. To test the hypothesis that peptides can be repeatedly detected and validated from fossil tissues many millions of years old, we applied updated extraction methodology, high-resolution mass spectrometry, and bioinformatics analyses on a Brachylophosaurus canadensis specimen (MOR 2598) from which collagen I peptides were recovered in 2009. We recovered eight peptide sequences of collagen I: two identical to peptides recovered in 2009 and six new peptides. Phylogenetic analyses place the recovered sequences within basal archosauria. When only the new sequences are considered, B. canadensis is grouped more closely to crocodylians, but when all sequences (current and those reported in 2009) are analyzed, B. canadensis is placed more closely to basal birds. The data robustly support the hypothesis of an endogenous origin for these peptides, confirm the idea that peptides can survive in specimens tens of millions of years old, and bolster the validity of the 2009 study. Furthermore, the new data expand the coverage of B. canadensis collagen I (a 33.6% increase in collagen I alpha 1 and 116.7% in alpha 2). Finally, this study demonstrates the importance of reexamining previously studied specimens with updated methods and instrumentation, as we obtained roughly the same amount of sequence data as the previous study with substantially less sample material. Data are available via ProteomeXchange with identifier PXD005087.


Helodermatid Lizard from the Mio-Pliocene Oak-Hickory Forest of Tennessee, Eastern USA, and a Review of Monstersaurian Osteoderms

Abstract: The extant venomous Gila monster and beaded lizards, species of Heloderma, live today in southwestern USA and south along the Pacific coastal region into Central America, but their fossil history is poorly understood. Here we report helodermatid osteoderms (dermal ossicles) from the late Miocene-early Pliocene Gray Fossil Site, eastern Tennessee USA. Twenty-three species of mammals are known from the fauna including abundant Tapirus polkensis, as well as fishes, anurans, salamanders, turtles, Alligator, birds, and snakes. Beaded lizards belong to the Monstersauria, a clade that includes Primaderma + Paraderma + Gobiderma + Helodermatidae (Estesia, Eurheloderma, Lowesaurus, and Heloderma). Osteoderms of lizards in this clade are unique within Squamata; they typically are circular to polygonal in outline, domed to flat-domed in cross-section, have a vermiculate surface texture, are not compound structures, and do not have imbricate surfaces as on many scincomorph and anguid lizards. We review and characterize the osteoderms of all members of Monstersauria. Osteoderms from the cranium, body, and limbs of Heloderma characteristically have a ring-extension (bony flange) at least partly surrounding the dome. Its presence appears to be a key character distinct to all species of Heloderma, consequently, we propose the presence of a ring-extension to be an apomorphy. Three osteoderms from the Gray Fossil Site range from 1.5 to 3.0 mm in diameter, have the circular shape of helodermatid osteoderms with a domed apical surface, and have the ring-extensions, permiting generic identification. Macrobotanical remains from the Gray Fossil Site indicate an oak-hickory subtropical forest dominated by Quercus (oak) and Carya (hickory) with some conifer species, an understorey including the climbing vines Sinomenium, Sargentodoxa, and Vitis. Plant and mammal remains indicate a strong Asian influence.


Late Miocene contourite channel system reveals intermittent overflow behavior

Abstract: Paleoceanographic information from submarine overflows in the vicinity of oceanic gateways is of major importance for resolving the role of ocean circulation in modulating Earth’s climate. Earth system models are currently the favored way to study the impact of gateways on global-scale processes, but studies on overflow-related deposits are more suitable to understand the detailed changes. Such deposits, however, had not yet been documented in outcrop. Here, we present a unique late Miocene contourite channel system from the Rifian Corridor (Morocco) related to the initiation of Mediterranean Outflow Water (MOW). Two channel branches were identified consisting of three vertically stacked channelized sandstone units encased in muddy deposits. Both branches have different channel-fill characteristics. Our findings provide strong evidence for intermittent behavior of overflow controlled by tectonic processes and regional climatic change. These fluctuations in paleo-MOW intermittently influenced global ocean circulation.


Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs

Abstract: The Ankylosauria is a group of herbivorous, quadrupedal, armoured dinosaurs subdivided into at least two major clades, the Ankylosauridae and the Nodosauridae. The most derived members of Ankylosauridae had a unique tail club formed from modified, tightly interlocking distal caudal vertebrae and enlarged osteoderms that envelop the terminus of the tail. We review all known ankylosaurid species, as well as ankylosaurs of uncertain affinities, in order to conduct a revised phylogenetic analysis of the clade. The revised phylogenetic analysis resulted in a monophyletic Ankylosauridae consisting of Ahshislepelta, Aletopelta, Gastonia, Gobisaurus, Liaoningosaurus, Shamosaurus and a suite of derived ankylosaurids (Ankylosaurinae). There is convincing evidence for the presence of nodosaurids in Asia during the Early Cretaceous. In the mid Cretaceous, Asian nodosaurids were replaced by ankylosaurine ankylosaurids. Ankylosaurines migrated into North America from Asia between the Albian and Campanian, where they diversified into a clade of ankylosaurines, here named Ankylosaurini, characterized by arched snouts and numerous flat cranial caputegulae. There is no evidence for any ankylosaurids in Gondwana; Ankylosauridae appears to be completely restricted to Asia and North America. The genus Crichtonpelta gen. nov. is created, type species Crichtonsaurus benxiensis Lü et al. http://zoobank.org/urn:lsid:zoobank.org:pub:EE5B88A3-3353-4FB6-B9A2-FCF0F99770EB

nodosauridae
tail club
osteoderm
ankylosaur