13-467: Austroptyctodus Campbellodus Chelyophorus Ctenurella Deinodus Destnoporella Eczematolepis Goniosteus Kimbryanodus Materpiscis Palaeomylus Ptyctodopsis Ptyctodus Rhamphodopsis Rhynchodus The ptyctodontids ("folded-teeth") are placoderms of the order Ptyctodontida , containing the family Ptyctodontidae . With their big heads, big eyes, reduced armor and long bodies,
26-518: A new species of the German genus Ctenurella . Long (1997) redescribed the German material and found major differences in the skull roof pattern so assigned it to a new genus, Austroptyctodus . This genus lacks spinal plates and has Ptyctodus -like toothplates. The most significant discovery about Austroptyctodus is that one specimen depicts a female pregnant with 3 unborn embryos inside her, showing that like Materpiscis , also from Gogo, this genus
39-551: Is a genus of ptyctodontid placoderm from the Late Devonian located at the Gogo Formation of Western Australia . Known from only one specimen, it is unique in having an unborn embryo present inside the mother, with remarkable preservation of a mineralised placental feeding structure ( umbilical cord ). This makes Materpiscis the oldest known vertebrate to show viviparity , or giving birth to live young. The holotype
52-627: The 1980s and '90's, ptyctodont skulls were compared with skulls from other orders. From these analyses, this idea of a gradient from least armored to most armored in placoderms was discarded. Now, the ptyctodonts are regarded as the sister group of the Arthrodira and Phyllolepida . Austroptyctodus Austroptyctodus gardineri is a small ptyctodontid placoderm fish from the Upper Devonian Gogo Formation of Western Australia . First described by Miles & Young (1977) as
65-527: The Ptyctodontida were not actually placoderms, but actual holocephalians, some primitive group of elasmobranch fish, or even were the ancestors of the holocephalians, including the chimaeras. Thorough anatomical examinations of whole fossil specimens reveal that the profound similarities between these two groups are actually very superficial. The major differences between them were that holocephalians have shagreen on their skin and ptyctodontids did not, that
78-421: The armored plates and scales of holocephalians are made of dentine , and the armored plates and scales of ptyctodontids were made of bone, the anatomy of the craniums of holocephalians is more similar to sharks, and that of ptyctodontids were more similar to those of other placoderms, and, most importantly, the holocephalians have true teeth, while the ptyctodonts had beak-like tooth-plates. The Ptyctodontida were
91-465: The holotype led to the discovery of the partially ossified skeleton of a juvenile Materpiscis and the mineralised umbilical cord. The team published their findings in 2008. The juvenile Materpiscis was about 25 percent of its adult size. The large size of the embryo relative to the mother indicates that the young of this fish were born well-formed, a strategy that may have evolved to counter predation from other larger fishes. The ptyctodontid fishes are
104-408: The only known group of placoderms that were recognizably sexually dimorphic , in that the males had hook-like growths on their pelvic fins that were analogous to the clasping organs found in male sharks, and chimaeras. Paleontologists believe that the males of the ancestral placoderm had pelvic claspers, but the claspers were lost in the evolutionary development of each of the placoderm orders, save for
117-448: The ptyctodontids (there are too few whole specimens of the primitive Stensioella heintzi to tell if the males of that species had claspers or not). Because they had reduced armor, the ptyctodontids were once thought to be the most primitive of the placoderms. Indeed, there has been the idea that the placoderms had a gradient, of sorts, from the least armored, and most primitive forms, to the heavily armored, most advanced forms. During
130-453: The ptyctodontids bore a superficial resemblance to modern day chimaeras ( Holocephali ). Their armor was reduced to a pattern of small plates around the head and neck. Like the extinct and related acanthothoracids , and the living and unrelated holocephalians , most of the ptyctodontids are thought to have lived near the sea bottom and preyed on shellfish . On account of their radically reduced armor, some paleontologists have suggested that
143-404: Was a live bearer that reproduced through internal fertilization . Austroptyctodus fossil individuals have ostracods recovered in the abdominal region. These ostracods were related to nocturnal ones, suggesting it hunted at night. This article about a placoderm is a stub . You can help Misplaced Pages by expanding it . Materpiscis Materpiscis ( Latin for mother fish )
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#1732854941911156-559: Was found in the Kimberley area of northern Western Australia by Lindsay Hatcher during the 2005 expedition to the Gogo led by John Long of Museum Victoria . Fossils from the Gogo Formation are preserved in limestone nodules, so dilute acetic acid is used to dissolve the surrounding limestone and reveal the fossil , often preserved in three dimensions with minimal distortion. The species
169-401: Was named Materpiscis attenboroughi in honour of David Attenborough who first drew attention to the significance of the Gogo fish sites in his 1979 series Life on Earth . Materpiscis would have been about 11 inches (28 cm) long and had powerful crushing tooth plates to grind up its prey, possibly hard shelled invertebrates like clams or corals. Examination of the tail section of
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