Pelvic claspers confirm chondrichthyan-like internal fertilization in arthrodires

  title={Pelvic claspers confirm chondrichthyan-like internal fertilization in arthrodires},
  author={Per Erik Ahlberg and Kate Trinajstic and Zerina Johanson and John Long},
Recent finds demonstrate that internal fertilization and viviparity (live birth) were more widespread in the Placodermi, an extinct group of armoured fishes, than was previously realized. Placoderms represent the sister group of the crown group jawed vertebrates (Gnathostomata), making their mode(s) of reproduction potentially informative about primitive gnathostome conditions. An ossified pelvic fin basipterygium discovered in the arthrodire Incisoscutum ritchiei was hypothesized to be… 

Pelvic and reproductive structures in placoderms (stem gnathostomes)

The morphology of the pelvic region within the arthrodires and ptyctodonts is reinterpreted and it is suggested that clasper position relative to the pelvic fins was determined by genes responsible for limb position.

Copulation in antiarch placoderms and the origin of gnathostome internal fertilization

It is shown that certain antiarchs possessed dermal claspers in the males, while females bore paired dermal plates inferred to have facilitated copulation, suggesting that external fertilization and spawning, which characterize most extant aquatic gnathostomes, must be derived from internal fertilization, even though this transformation has been thought implausible.

Hyperossification in the Vertebral Column of Devonian Placoderm Fishes (Arthrodira)

Hyperossifcation in these arthrodires demonstrates that increases in endoskeletal bone mass are not restricted to crown-group gnathostomes (Chondrichthyes + Actinopterygii), representing a first step in the evolution of this process, involving modifications to cortical bone layers.

A preliminary note of egg-case oviparity in a Devonian placoderm fish

Six enigmatic fossils from the Famennian (Devonian) Cleveland Shale in Ohio, U.S.A., are interpreted here as arthrodiran (Placodermi) egg cases, representing the first record for a non-chondrichthyan producer and suggesting external fertilization as the primitive gnathostome reproductive mode.

A New Selenosteid Arthrodire (‘Placodermi’) from the Late Devonian of Morocco

A new phylogenetic hypothesis supports the monophyly of the Selenosteidae within which this new taxon is resolved, but emphasizes also unresolved relationships among aspinothoracid arthrodires.

New Morphological Information on the Ptyctodontid Fishes (Placodermi, Ptyctodontida) from Western Australia

ABSTRACT A full description of a complete and articulated, three-dimensionally preserved, placoderm fish, Materpiscis attenboroughi (Ptyctodontida), from the Late Devonian Gogo Formation is

New morphological information on, and species of placoderm fish Africanaspis (Arthrodira, Placodermi) from the Late Devonian of South Africa

There is some faunal overlap between the Waterloo Farm fossil site and faunas described from Strud in Belgium and Red Hill, Pennsylvania, in north America, supporting the concept of a more cosmopolitan vertebrate fauna in the Famennian than earlier in the Devonian.

The characters of Palaeozoic jawed vertebrates

A clearly stated hierarchy of synapomorphies covering the jaw-bearing stem gnathostomes and osteichthyan and chondrichthyan stem groups is provided and a proposed synapomorphy scheme is used to evaluate the status of the problematic fossil groups Acanthodii and Placodermi.

Evolution of vertebrate postcranial complexity: axial skeleton regionalization and paired appendages in a Devonian jawless fish

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Devonian arthrodire embryos and the origin of internal fertilization in vertebrates

It is shown that Incisoscutum and some phyllolepid arthrodires possessed pelvic girdles with long basipterygia that articulated distally with an additional cartilaginous element or series, as in chondrichthyans, indicating that the pelvic fin was used in copulation.

Live birth in the Devonian period

The oldest record of a live-bearing vertebrate in a new ptyctodontid placoderm, Materpiscis attenboroughi gen. et sp.

Observations on the ptyctodont fish, Rhamphodopsis Watson

The occurrence of strong sexual dimorphism in the pelvic region is confirmed, and descriptions are given of the ‘claspers' in males, and of the large scale-bearing pelvic fins and their endoskeleton in females.

The braincase and jaws of a Devonian ‘acanthodian’ and modern gnathostome origins

The first-known braincase of an Early Devonian acanthodian is presented, andylogenetic analysis resolves Ptomacanthus as either the most basal chondrichthyan or as the sister group of all living gnathostomes, to provide a more detailed picture of the acquisition of early Gnathostome characters.


“Recent Advances in the Origin and Early Radiation of Vertebrates” honors Dr. Hans-Peter Schultze for his influential body of work on lower vertebrates spanning the past 40 years, and counting. The

Observations on the ptyctodont fish

  • Rhamphodopsis Watson. J. Linn. Soc. London Zool
  • 1967