Ben Creisler
Some recent (and not so recent) non-dino papers that may be of interest:
A paper from last year not yet mentioned. I can only find a Research Gate link for the full article:
Ralf Werneburg (2017)
Earliest nursery ground of temnospondyl amphibians in the Permian.
Semana 32: 3-42
The nursery ground of the Obermoschel-lake forms a keystone in understanding of earliest larval development in temnospondyl amphibians. This temnospondyl fauna of Obermoschel in the Saar-Nahe Basin (Rotliegend, Lower Permian, Sakmarian) permits new insights for ontogeny â with stages of 0.1 mm intervals. In total, 35 specimens have a skull length from 0.8 mm to 2.0 mm and a body length from 5.2 mm up to 17.2 mm. An important step in character development started in this earliest larval phase with a skull length from 1 to 2 mm. About 60 of more than 200 larval specimens were selected for drawings and descriptions. The larvae of the branchiosaurids Apateon pedestris and A. caducus as well as of the stereospondylomorph Sclerocephalus haeuseri represent stages with skull lengths of 0.8 up to 7.4 mm. The most reliable feature to distinguish the early larvae of both branchiosaurid species is the onset of ossification, development of the humerus as well as the shape of basibranchial, hyohyal, interclavicle and the intraorbital width. The difference in the width of the tooth base between branchiosaurids and S. haeuseri is obvious. The large, elongated interclavicle of S. haeuseri with a skull length of 2.4 mm has a triangular posterior margin with nearly a right angle, which represents a clear cut difference to branchiosaurids and Micromelerpeton credneri.
Among species, detailed comparisons of ossification sequences are necessary for a better understanding of evolutionary change in ontogeny. The ossification sequence of the same species differs dramatically from lake to lake. It illustrates the plastic response of the two branchiosaurid species to the changing living conditions in the lakes and is considered as a case of intraspecific heterochrony. The ossification sequence of A. pedestris and A. caducus is nearly identical in the Obermoschel-lake; however, skull length differs between both species at the first appearance of the bones at 0.2 and 0.4 mm. The ossification sequence of S. haeuseri and of branchiosaurids is, in many cases, very similar, but some exceptions exist. The first appearance of distinct bones started long before in S. haeuseri than in M. credneri. A chronology of four larval phases is newly established. Diagnostic features in the early larval stages (Sl=1-7 mm) are presented for A. pedestris, A. caducus and for S. haeuseri.
The wide cultriform process is a key feature of salamanders, which is discovered in the earliest larvae of branchiosaurids and of S. haeuseri herein. Additionally, the branchiosaurid cultriform process shows in few specimens an anteromedian concave end, which is characteristic for the salamanders as well. The âembryo-lengthâ and âegg diametersâ are very similar in branchiosaurids and extant newts, but the âembryo-lengthâ and âegg diameterâ of S. haeuseri are significantly smaller than in the extant giant salamanders in spite of same adult size.
The first complete record of the branchiosaurid hyobranchium with calcareous ceratohyal and ceratobranchials is discovered in A. caducus. The longitudinal color strips of the body may indicate the color pattern of the skin in the branchiosaurids A. pedestris, A. caducus and S. haeuseri. The slender tail fin and the short external gills characterise one ecomorphotype of branchiosaurs - the stream-type - living in fluvial oxygen-rich turbulent and quiet water environments.
Some early larvae are known from the Rotliegend (Lower Permian) of the Thuringian Forest basin, namely specimens of A. dracyi from the Lake Cabarz starting with the skull length of 1.8 to 1.9 mm and of A. flagrifer/M. gracile from the Lake Wintersbrunnen with a skull length of 2.3 to 3.9 mm. The ossification sequence of A. dracyi from the Cabarz-lake and A. pedestris from the Obermoschel-lake shows nearly the same order of bone formations.
A short review on the smallest known larvae in temnospondyls and anthracosaurs is provided to stimulate further investigations of ontogeny.
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AndrÃs SolÃrzano, Ascanio D. RincÃn, Giovanne M. Cidade, MÃnica NÃÃez-Flores & Leonardo SÃnchez (2018)
Lower Miocene alligatoroids (Crocodylia) from the Castillo Formation, northwest of Venezuela.
Palaeobiodiversity and Palaeoenvironments (advance online publication)
Crocodyliform diversity was particularly high during the middle and late Miocene of South America, with up to 12 species recovered from a single geological unit. Nonetheless, the early Miocene fossil record of low-latitude vertebrates is scarce; hence, crocodylians remain poorly known in the region. The Castillo Formation, located in the northwest of Venezuela, preserves an interesting vertebrate fauna with a well-constrained late early Miocene age. Previous work dealing with crocodylians of this formation only recorded three taxa: the gavialoid Siquisiquesuchus venezuelensis and Gryposuchus sp. and indeterminate alligatoroid remains. New cranial and mandibular material recently recovered from the Castillo Formation allows us to document four previously unrecognised alligatoroid forms: Purussaurus sp., Caiman sp., an indeterminate caimanine and an indeterminate alligatoroid. With six taxa, the crocodylian assemblage reveals a previously undocumented relatively high taxonomic diversity in the early Miocene. The Castillo crocodylians show a broad range of morphological disparity and body sizes ranging from small (2.5 mâ62 kg) to large (7.5 mâ1600 kg) taxa. Thus, crocodylian niche partition, as well as the abundance and variety of resources and environmental heterogeneity of aquatic ecosystems in South America, were already established by at least the early Miocene. The presence of Caiman in ~â18 Ma strata represents the unequivocally earliest record of the taxon in South America and allows us to propose that the origin of the jacareans is more likely to have occurred during or before the early Miocene, challenging previous molecular hypotheses.
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GÃnter P. Wagner, Oliver W. Griffith, Philip J. Bergmann, Gaelle BelloâHellegouarch, Tiana Kohlsdorf, Anjan Bhullar & Cameron D. Siler (2018)
Are there general laws for digit evolution in squamates? The loss and reâevolution of digits in a clade of fossorial lizards (Brachymeles, Scincinae).
Journal of Morphology (advance online publication)
Evolutionary simplification of autopodial structures is a major theme in studies of bodyâform evolution. Previous studies on amniotes have supported Morse's law, that is, that the first digit reduced is Digit I, followed by Digit V. Furthermore, the question of reversibility for evolutionary digit loss and its implications for "Dollo's law" remains controversial. Here, we provide an analysis of limb and digit evolution for the skink genus Brachymeles. Employing phylogenetic, morphological, osteological, and myological data, we (a) test the hypothesis that digits have reâevolved, (b) describe patterns of morphological evolution, and (c) investigate whether patterns of digit loss are generalizable across taxa. We found strong statistical support for digit, but not limb reâevolution. The feet of pentadactyl species of Brachymeles are very similar to those of outgroup species, while the hands of these lineages are modified (2â3â3â3â2) and a have a reduced set of intrinsic hand muscles. Digit number variation suggests a more labile Digit V than Digit I, contrary to Morse's law. The observed pattern of digit variation is different from that of other scincid lizards (Lerista, Hemiergis, Carlia). Our results present the first evidence of cladeâspecific modes of digit reduction.
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Oleksandr Yaryhin & Ingmar Werneburg (2018)
Tracing the developmental origin of a lizard skull: Chondrocranial architecture, heterochrony, and variation in lacertids.
Journal of Morphology (advance online publication)
The sand lizard, Lacerta agilis, is a classical model species in herpetology. Its adult skull anatomy and its embryonic development are well known. The description of its fully formed primordial skull by Ernst Gaupp, in 1900, was a key publication in vertebrate morphology and influenced many comparative embryologists. Based on recent methodological considerations, we restudied the early cranial development of this species starting as early as the formation of mesenchymal condensations up to the fully formed chondrocranium. We traced the formation of the complex chondrocranial architecture in detail, clarified specific homologies for the first time, and uncovered major differences to old textbook descriptions. Comparison with other lacertid lizards revealed a very similar genesis of the primordial skull. However, we detected shifts in the developmental timing of particular cartilaginous elements, mainly in the nasal region, which may correlate to specific ecological adaptation in the adults. Late timing of nasal elements might be an important innovation for the successful wide range distribution of the wellâknown sand lizard.
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Mariana B. J. Picasso & Claudio Gustavo Barbeito (2018)
Hindlimb bone maturation during postnatal life in the Greater Rhea (Rhea americana, Aves, Palaeognathae): Implications for palaeobiological and zooarchaeological interpretations.
Anatomia, Histologia, Embryologia (advance online publication)
The objective of this study was to study the morphological pattern of bone maturation of the hindlimb bones of Rhea americana and find out how it can affect bone morphology after a taphonomic process. Juvenile specimens (n = 10) ranging from one month old to eight months old were studied. For comparison, bones from adults and juveniles from museum specimens (n = 4 and n = 6, respectively) were studied. In fresh bones, ossification centres were identified in the proximal and distal epiphyses of the tibiotarsi and in the proximal epiphysis of the tarsometatarsi, whereas the distal region of the femora and tarsometatarsi showed abundance of cartilage. The development and extension of the ossification centres of the tibiotarsi were different. In the proximal epiphysis, the centre presented less development with respect to the distal epiphysis. In the dry tibiotarsi, the proximal centre was absent and the distal one was well preserved. Both the fresh and dry juvenile tarsometatarsi presented unfused metatarsals and bulkier and wider aspect than the adult ones. The dry femora presented a noticeable excavation between condyles, whereas the dry tarsometatarsi showed the absence of the proximal epiphysis. The femora, tibiotarsi and tarsometatarsi possessed different traits of immaturity, which differentially affect the morphology of the preserved bones during a taphonomic process.
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James D. Witts , Neil H. Landman, Matthew P. Garb, Caitlin Boas, Ekaterina Larina, Remy Rovelli, Lucy E. Edwards, Robert M. Sherrell & J. Kirk Cochran (2018)
A fossiliferous spherule-rich bed at the CretaceousâPaleogene (KâPg) boundary in Mississippi, USA: Implications for the KâPg mass extinction event in the Mississippi Embayment and Eastern Gulf Coastal Plain.
Cretaceous Research (advance online publication)
Highlights
Describes new outcrops containing the CretaceousâPaleogene (KâPg) boundary from Union County, Mississippi.
The fossiliferous Owl Creek Formation contains ammonites and diverse benthic molluscan fauna.
Biostratigraphic correlation by macro and microfossils is consistent with deposition during the latest Maastrichtian.
A 15â30 cm-thick event bed with macrofossils and impact spherules occurs above the KâPg boundary.
Spherule bed was emplaced rapidly by multiple processes following the Chicxulub impact event.
Abstract
We describe an outcrop of the CretaceousâPaleogene (KâPg) boundary exposed due to construction near New Albany, Union County, Mississippi. It consists of the Owl Creek Formation and overlying Clayton Formation. The Owl Creek Formation is rich in the ammonites Discoscaphites iris and Eubaculites carinatus, which, along with biostratigraphically important dinoflagellate cysts and calcareous nannofossils, indicate deposition occurred within the last 1 million years, most likely last 500 kyrs, of the Cretaceous. The base of the overlying Clayton Formation marks the KâPg boundary, and consists of a 15â30 cm thick muddy, poorly sorted quartz sand containing abundant spherules representing ejecta derived from the Chicxulub impact event. Impact spherules range in size from 0.5 mm to 1 mm in diameter and are hollow and well preserved, with details such as smaller vesicular spherules enclosed within. The spherules are altered to clay minerals such as smectite and are typical of those found at KâPg boundary sites in the Gulf of Mexico and beyond. Spherules are scattered throughout the bed, and surface counts suggest an average of 4 spherules per cm2. Macrofossils within the spherule bed represent a rich fauna of ammonites, benthic molluscs (bivalves and gastropods), echinoids, as well as crabs and sharks. Macrofossil preservation ranges from whole to fragmentary, with most fossils preserved as internal moulds. The infill of the fossils is lithologically identical to the matrix of the spherule bed, including impact ejecta preserved within phragmocones and body chambers of ammonites, and differs from the underlying Owl Creek Formation. This suggests that the animals were either alive or loosely scattered on the sea floor at the time of deposition. Grain size changes indicate multiple events were responsible for deposition, and together with taphonomic evidence are consistent with dynamic high energy post-impact processes. Later sea level change during the Paleocene is responsible for a sharp contact at the top of the spherule bed. Geochemical evidence from the Owl Creek and Clayton Formations at this locality indicate numerous local paleoenvironmental changes affected the Mississippi Embayment at the time of the KâPg boundary and mass extinction event.
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