''Tropidosteus curvatus'' is a large, extinct holonematid arthrodire placoderm from the Givetian-aged Crinoidenmergel stratum of Middle

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

Rheinland The Rhineland (german: Rheinland; french: Rhénanie; nl, Rijnland; ksh, Rhingland; Latinised name: ''Rhenania'') is a loosely defined area of Western Germany along the Rhine, chiefly its middle section. Term Historically, the Rhinelands ...

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. ''T. curvatus'' is known from primarily from a slender, 42 centimeter long, arched median dorsal plate, where the two sides meet at a sixty to ninety degree angle, which would have given the live animal a humped appearance. The median dorsal plate is very similar to the median dorsal plates of '' Rhenonema'' and '' Belemnacanthus'', and is the primary reason for ''T. curvatus''' placement within Holonematidae. After stating this reason, Denison, 1978, then questions ''Tropidosteus placement within the family, noting that the dorsal plate lacks ridged ornamentation, which is a key diagnostic trait of the family. The ornamentation otherwise consists of an external covering of small tubercles.

References

Holonematidae Placoderms of Europe {{Placoderm-stub