Mitrate

Mitrate Temporal range: Cambrian–Carboniferous (500–360 Ma)[1] PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Echinodermata
Class:	†Stylophora
Order:	†Mitrata Jaekel, 1918

Mitrates are an extinct group of

The organisms were a few millimetres long.[1] Like the echinoderms, they are covered in armour plates, each of which comprises a single crystal of calcite. This is one of the features they share with the latter group, along with a water vascular system, only discovered in 2019.^[2] However, they do not display the familiar fivefold symmetry that more recent echinoderms possess, instead being close to (but not fully) bilaterally symmetrical.^[1][3]

Their heads had two sides; one, flat, was covered with large "pavement-like"^[1] plates, the other, convex, bore smaller plates.^[1] Their tails were long and segmented, resembling the stalk of a crinoid or the arm of a brittlestar.^[1] At the opposite end was a hole which may have been mouth or anus - or both.^[1]

They also bear features reminiscent of pharyngeal slits,^[4] a character lost in other echinoderms but present in hemichordates,^[1] causing R.P.S. Jefferies to hold them as the ancestor of all chordates.

Behaviour

Mitrates^ have been found with associated trace fossils.^[5][6] Their interpretation requires an understanding of how the animal was oriented in life; it's not agreed whether the convex side of the head was up or down, or indeed whether the "tail" was at the front or back of the organism.^[1] The trace fossils suggest that they pulled themselves through the mud with their "tail", and were flat-side up.^[1]

Notes

^ Rhenocystis latipedunculata

References

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