Styracopterid ( A ctinopterygii) ontogeny and the multiple origins of post‐ H angenberg deep‐bodied fishes

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99621/1/zoj12054.pd

An examination of the Devonian fishes of Michigan

We surveyed the taxa, ecosystems, and localities of the Devonian fishes of Michigan to provide a framework for renewed study, to learn about the diversity and number of these fishes, and to investigate their connection to other North American faunas. Nineteen genera of fishes have been found in the Middle and Late Devonian deposits of Michigan, of which thirteen are ‘placoderms’ represented by material ranging from articulated head shields to ichthyoliths. As expected from the marine nature of these deposits, ‘placoderms’ are overwhelmingly arthrodire in nature, but two genera of ptyctodonts have been reported along with less common petalichthyid material. The remaining fish fauna consists of fin-spines attributed to ‘acanthodians’, two genera of potential crown chondrichthyans, an isolated dipnoan, and onychodont teeth/jaw material. There was an apparent drop in fish diversity and fossil abundance between Middle and Late Devonian sediments. This pattern may be attributed to a paucity of Late Devonian sites, along with a relative lack of recent collection efforts at existing outcrops. It may also be due to a shift towards open water pelagic environments at Late Devonian localities, as opposed to the nearshore reef fauna preserved in the more numerous Middle Devonian localities. The Middle Devonian vertebrate fauna in Michigan shows strong connections with same-age assemblages from Ohio and New York. Finally, we document the presence of partially articulated vertebrate remains associated with benthic invertebrates, an uncommon occurrence in Devonian strata outside of North America. We anticipate this new survey will guide future field work efforts in an undersampled yet highly accessible region that preserves an abundance of fishes from a critical interval in marine vertebrate evolution

The nearshore cradle of early vertebrate diversification

Ancestral vertebrate habitats are subject to controversy and obscured by limited, often contradictory paleontological data. We assembled fossil vertebrate occurrence and habitat datasets spanning the middle Paleozoic (480 million to 360 million years ago) and found that early vertebrate clades, both jawed and jawless, originated in restricted, shallow intertidal-subtidal environments. Nearshore divergences gave rise to body plans with different dispersal abilities: Robust fishes shifted shoreward, whereas gracile groups moved seaward. Fresh waters were invaded repeatedly, but movement to deeper waters was contingent upon form and short-lived until the later Devonian. Our results contrast with the onshore-offshore trends, reef-centered diversification, and mid-shelf clustering observed for benthic invertebrates. Nearshore origins for vertebrates may be linked to the demands of their mobility and may have influenced the structure of their early fossil record and diversification

Styracopterus Traquair 1890

STYRACOPTERUS TRAQUAIR, 1890 Type and only species: Styracopterus fulcratus (Traquair, 1881). Diagnosis (emended from Gardiner, 1985): Styracopterid eurynotiform fish with two smooth ganoine bands on jaw margins of maxilla and dentary; maxilla with right-triangle-shaped posterior expansion and pointed anterior ramus; dentary shallow with angled anterior margin; mandibular canal pores large; maxillary teeth large and fang-like with a visible collar marking acrodin caps; palatal tooth-plate denticles large, stout, and rounded; mandibular tooth plate denticles small and rectangular; premaxilla fused to rostral; frontals with sigmoidal lateral margin; parietals triangular with sigmoidal lateral margin; dermopterotic curved laterally; post-temporal broad; suspensorium near vertical; preoperculum vertical with straight margins; opercular rectangular; subopercular taller than opercular with straight posterior margin; broad patches and bands of smooth ganoine over pointed anterior ramus; flank scales tall with ornament of nested ridges dorsally and horizontal ridges ventrally; dorsal ridge scales with thick horizontal ornament; ventral ridge scales near skull; pectoral fin long and scythe-shaped with broad leading lepidotrichia bearing rectangular segments; pelvic fin small and triangular with single preceding basal fulcrum; anal fin subtriangular with straight posterior margin. Occurrence: Early Visean of Scotland.Published as part of Sallan, Lauren Cole & Coates, Michael I., 2013, Styracopterid (Actinopterygii) ontogeny and the multiple origins of post-Hangenberg deep-bodied fishes, pp. 156-199 in Zoological Journal of the Linnean Society 169 (1) on pages 158-159, DOI: 10.1111/zoj.12054, http://zenodo.org/record/528662

Actinopterygii COPE 1881

ACTINOPTERYGII COPE, 1881 EURYNOTIFORMES (NOV.) Type genus: Eurynotus Agassiz, 1833 –1844. Included genera: Eurynotus Agassiz, 1833 –1844, Styracopterus Traquair, 1890, Fouldenia White, 1927, Benedenius Traquair, 1878, Amphicentrum Young, 1866, Cheirodopsis Traquair, 1881, Paramesolepis Moy-Thomas & Bradley Dyne, 1938, Wardichthys Traquair, 1875, Proteurynotus Moy-Thomas & Bradley Dyne, 1938, Mesolepis Young, 1866. Diagnosis: Actinopterygians with tall rectangular trunk scales bearing central pointed pegs at least 50% height of scale; jaw margins covered with thick ganoine and without visible teeth; premaxilla edentulous; dentary edentulous; maxillary dentition mesial to jaw margin and obscured laterally by dermal bone; palatal and mandibular tooth plates with denticles; maxilla with triangular posterior expanded portion and thick anterior ramus; mandible robust with acute symphysis in lateral aspect; snout blunt in lateral profile; preoperculum tall with horizontal pit line; suboperculum with anteroventral process; dorsal ridge scales prominent and acuminate, running from skull to dorsal fin origin; basal fulcra erect and pointed; median fins with longest fin ray more than fourth in position from leading edge; primary median fin lepidotrichia spine-like and without clear segments; fringing fulcra prominent, pointed, and overlapped distally on all fins. Symplesiomorphies: antorbitals absent; single median rostral; single nasal in contact with frontal and dermosphenotic; frontals longer than parietals; dermopterotic present; uninterrupted contact between preopercular and infraorbitals; supraorbitals absent; dermohyal present; single postcleithrum; axial lobe extending beyond caudal fin and axial fulcra with micromeric elliptical scales; epichordal fin present and distinct from caudal fin.Published as part of Sallan, Lauren Cole & Coates, Michael I., 2013, Styracopterid (Actinopterygii) ontogeny and the multiple origins of post-Hangenberg deep-bodied fishes, pp. 156-199 in Zoological Journal of the Linnean Society 169 (1) on page 158, DOI: 10.1111/zoj.12054, http://zenodo.org/record/528662

Early amphibians evolved distinct vertebrae for habitat invasions.

Living tetrapods owe their existence to a critical moment 360-340 million years ago when their ancestors walked on land. Vertebrae are central to locomotion, yet systematic testing of correlations between vertebral form and terrestriality and subsequent reinvasions of aquatic habitats is lacking, obscuring our understanding of movement capabilities in early tetrapods. Here, we quantified vertebral shape across a diverse group of Paleozoic amphibians (Temnospondyli) encompassing different habitats and nearly the full range of early tetrapod vertebral shapes. We demonstrate that temnospondyls were likely ancestrally terrestrial and had several early reinvasions of aquatic habitats. We find a greater diversity in temnospondyl vertebrae than previously known. We also overturn long-held hypotheses centered on weight-bearing, showing that neural arch features, including muscle attachment, were plastic across the water-land divide and do not provide a clear signal of habitat preferences. In contrast, intercentra traits were critical, with temnospondyls repeatedly converging on distinct forms in terrestrial and aquatic taxa, with little overlap between. Through our geometric morphometric study, we have been able to document associations between vertebral shape and environmental preferences in Paleozoic tetrapods and to reveal morphological constraints imposed by vertebrae to locomotion, independent of ancestry

Database S1

Database S1: Downloaded datasets from the Paleobiology Database, regional paleocommunity records from Boucot and Lawson, all input files and trees in nexus, txt and csv format, R code for analyses and figures, and all results files

The ‘Tully Monster’ is not a vertebrate:characters, convergence and taphonomy in Palaeozoic problematic animals

The affinity of Tullimonstrum gregarium, a pincer-mouthed, soft bodied bilaterian, has been subject to debate since its recovery from Carboniferous coal deposits at Mazon Creek, Illinois. After decades of impasse focused on mollusc, arthropod and annelid attributes, two recent, yet conflicting, high-profile studies concluded that the ‘Tully Monster’ is a vertebrate, a relative of lampreys or jawed fishes. Here, we find that structures described as supporting vertebrate – particularly crown vertebrate – affinity face significant challenges from biological, functional and taphonomic perspectives. Problems with comparator choice, interpretation of taphonomic processes at Mazon Creek, and estimation of convergence within the bilaterian tree may have misled these recent studies, leading to conclusions which do not accommodate current understanding of the vertebrate record. For example, the absence of taphonomically-expected synapomorphies in Tullimonstrum (e.g. otic capsules, body pigment) calls into question vertebrate identity and implies that convergence or deeper origins are responsible for vertebrate-like traits. Further, phylogenetic placement within vertebrates is only made possible by the constraints of a chordate-only dataset with limited outgroups and use of selective characters. Long-discussed alternative placements among molluscs (e.g. heteropod gastropods), arthropods (e.g. anomalocarids), or elsewhere within non-vertebrate deuterostomes are more congruent. Indeed, many of these lineages independently evolved vertebrate-like traits, including complex eyes and ‘teeth’. Thus, given the totality of evidence, Tullimonstrum should be excluded from the vertebrate crown. Potential assignments for aberrant bilaterians, common throughout the Palaeozoic fossil record, need be considered in light of the number and likelihood of required exceptions to established schemes

Analysis scripts and data

Includes phylogenetic trees, evolutionary rate estimates, geographic data, and scripts to repeat all analyses from article