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Very common placoderm at Red Hill site, but rarely articulated. Diagnosis. A small groenlandaspidid with a short head shield and tall and narrow dorsal trunk elements. The head shield is almost as wide as long (average W/L equals 0.96). The pineal is divided into two distinct plates in every specimen and the postmarginal makes contact with the postorbital plate, excluding the marginal plate from the lateral margin of the head shield. A continuation of the supraorbital sensory line reaches the caudal margin of the paranuchal plate. The PDL has an average H/L ratio of 2.42. The posterodorsal projection of the PDL is short and angled sharply upward so that the overlap zone for the MD does not reach the caudal margin of the element. The height of the symphysial area on the visceral surface of the PDL is 40% of the total height of the element. The MD is also high and narrow and approximately equal in height to the PDL. The MD has numerous coarse serrations along the caudal margin and tubercles on the lateral surfaces that form rows parallel to the ventral margin. ADL, anterior dorsolateral plate; AL, anterior lateral plate; AMV, anterior median ventral plate; APi, anterior pineal plate; AVL, anterior ventrolateral plate; Ce, central plate; IL, interolateral plate; M, marginal plate; MD, median dorsal plate; Nu, nuchal plate; PDL, posterior dorsolateral plate; Pi, pineal plate; PL, posterior lateral plate; PM, postmarginal plate; PMV, posterior median ventral plate; PNu, paranuchal plate; PPi, posterior pineal plate; PrO, preorbital plate; Psp, parasphenoid; PtO, postorbital plate; PVL, posterior ventrolateral plate; R, rostral plate; Sgn, supragnathal; SP, spinal plate. EDWARD B. DAESCHLER,1* ANNA C. FRUMES2 AND C. FREDERICK MULLISON1 Records of the Australian Museum (2003) Vol. 55: 45–60. ISSN 0067-1975
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From the album: Misha's Late Devonian Fossils
Arthrodire placoderm bone Unknown species Found near the boundary of the marine Catskill and Lock Haven Fms in light gray colored sandstone Unfortunately the bone was very weathered and fell apart while splitting down the matrix, this is what I was able to piece back together. Lock Haven Formation Frasnian-Fammenian Pennsylvania-
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Wolf Run Preserve along the Vermilion River may well harbor fossils of the fearsome Dunkleosteus (photo gallery) Peter Krouse, ClevelandCom, February. 07, 2022 More about Dunkleosteus: A Devonian Fish Tale: A New Method of Body Length Estimation Suggests Much Smaller Sizes for Dunkleosteus terrelli (Placodermi: Arthrodira) Diversity 15(3):318, February 2023 Paleobiology of Dunkleosteus terrelli and Paleoecology of the Cleveland Shale Yours, Paul H.
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From the album: Vertebrates
Millerosteus minor Miller, 1858 Middle Devonian Eifelian Caithness Scotland Millerosteus minor (named after Hugh Miller, a Scottish geologist and paleontologist 1802-1856) was a small arthrodire placoderm, rarely exceeding 15cm. The extinct armored fishes known as placoderms make up what is considered to be the earliest branch of the gnathostome family tree -- the earliest branch of the jawed fishes. Arthrodires possessed jaws but no teeth. Razor-sharp bony dental plates formed sort of a beak and allowed to gnaw on prey. Arthrodires (“jointed neck”) are characterized by an unusual joint in the dorsal armor between the head and neck regions; this joint apparently allowed the head to move upwards as the jaw dropped downwards, creating a larger gape. In addition, it also had an internal joint between its neck vertebrae and the back of the skull, allowing for the mouth to be opened even wider and being able to feed on rather large prey. Millerosteus probably fed on invertebrates such as crustaceans and mollusks or even was a mud-grubber that ingested organic-rich mud for its food. Arthrodires possessed a heavily armored head- and neck-region. The slender fish-like body and the heterocercal tail that extends behind the heavily armored portion is, because it is almost naked or only covered with small scales, rarely preserved. Millerosteus is a rather common fish in the Middle Devonian flagstones around Caithness.-
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G'day, We recently found this partial placoderm skull at a property near Wee Jasper, NSW and I'm wondering what part of the skull it is. We found a lot of other stuff on that trip too, and I'll do a trip report on that eventually. Thanks, Izak
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