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Abstract We describe an exceptionally well-preserved vampyropod,Syllipsimopodi bidenigen. et sp. nov., from the Carboniferous (Mississippian) Bear Gulch Lagerstätte of Montana, USA. The specimen possesses a gladius and ten robust arms bearing biserial rows of suckers; it is the only known vampyropod to retain the ancestral ten-arm condition.Syllipsimopodiis the oldest definitive vampyropod and crown coleoid, pushing back the fossil record of this group by ~81.9 million years, corroborating molecular clock estimates. Using a Bayesian tip-dated phylogeny of fossil neocoleoid cephalopods, we demonstrate thatSyllipsimopodiis the earliest-diverging known vampyropod. This strongly challenges the common hypothesis that vampyropods descended from a Triassic phragmoteuthid belemnoid. As early as the Mississippian, vampyropods were evidently characterized by the loss of the chambered phragmocone and primordial rostrum—traits retained in belemnoids and many extant decabrachians. A pair of arms may have been elongated, which when combined with the long gladius and terminal fins, indicates that the morphology of the earliest vampyropods superficially resembled extant squids.
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Tanyrhinichthys mcallisteri, a long-rostrumed Pennsylvanian ray-finned fish (Actinopterygii) and the simultaneous appearance of novel ecomorphologies in Late Palaeozoic fishes
Abstract The Carboniferous radiation of fishes was marked by the convergent appearance of then-novel but now common ecomorphologies resulting from changes in the relative proportions of traits, including elongation of the front of the skull (rostrum). The earliest ray-finned fishes (Actinopterygii) with elongate rostra are poorly known, obscuring the earliest appearances of a now widespread feature in actinopterygians. We redescribe Tanyrhinichthys mcallisteri, a long-rostrumed actinopterygian from the Upper Pennsylvanian (Missourian) of the Kinney Brick Quarry, New Mexico. Tanyrhinichthys has a lengthened rostrum bearing a sensory canal, ventrally inserted paired fins, posteriorly placed median fins unequal in size and shape, and a heterocercal caudal fin. Tanyrhinichthys shares these features with sturgeons, but lacks chondrostean synapomorphies, indicating convergence on a bottom-feeding lifestyle. Elongate rostra evolved independently in two lineages of bottom-dwelling, freshwater actinopterygians in the Late Pennsylvanian of Euramerica, as well as in at least one North American chondrichthyan (Bandringa rayi). The near-simultaneous appearance of novel ecomorphologies among multiple, distantly related lineages of actinopterygians and chondrichthyans was common during the Carboniferous radiation of fishes. This may reflect global shifts in marine and freshwater ecosystems and environments during the Carboniferous favouring such ecomorphologies, or it may have been contingent on the plasticity of early actinopterygians and chondrichthyans.
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- Award ID(s):
- 1846777
- PAR ID:
- 10183356
- Date Published:
- Journal Name:
- Zoological Journal of the Linnean Society
- ISSN:
- 0024-4082
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/zoolinnean/zlaa044
