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Hirnantia sagittifera

Rhynchonellata - Orthida - Draboviidae

Taxonomy
Orthis sagittifera was named by McCoy (1851). It is a 3D body fossil. It is the type species of Hirnantia.

It was recombined as Hirnantia sagittifera by Lamont (1935), Cocks (1982), Brenchley et al. (2006), Jin and Zhan (2008), Hints et al. (2012) and Hints and Harper (2015).

Synonymy list
YearName and author
1851Orthis sagittifera McCoy
1935Hirnantia sagittifera Lamont p. 313
1982Hirnantia sagittifera Cocks pp. 763 - 764 figs. Plate 78, figs. 6-10; Plate 79, figs. 1-3; Plate 80, fig. 8
2006Hirnantia sagittifera Brenchley et al. p. 16 figs. 12A, C, F
2008Hirnantia sagittifera Jin and Zhan pp. 52-53 figs. Pl. 36, figs. 1-16
2012Hirnantia sagittifera Hints et al. pp. 67 - 70 fig. 2
2015Hirnantia sagittifera Hints and Harper

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RankNameAuthor
kingdomAnimalia()
Triploblastica
Eutriploblastica
Neotriploblastica
Eucoelomata
superphylumLophotrochozoa
Lophophorata
phylumBrachiopodaCuvier 1805
subphylumRhynchonelliformeaWilliams et al. 1996
RankNameAuthor
classRhynchonellataWilliams et al. 1996
orderOrthidaSchuchert and Cooper 1932
suborderDalmanellidinaMoore 1952
superfamilyEnteletoideaWaagen 1884
familyDraboviidaeHavlicek 1950
subfamilyDraboviinaeHavlicek 1950
genusHirnantiaLamont 1935
speciessagittifera(McCoy 1851)

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

Diagnosis
ReferenceDiagnosis
L. R. M. Cocks 1982Exterior. Biconvex, with convexity of brachial valve considerably greater than pedicle valve. Faint trace of very weak pedicle valve fold and corresponding brachial valve sulcus seen in a few valves only. Small anacline brachial valve interarea ยท and fairly small apsacline pedicle interarea. Open delthyrium with small pedicle collar and open notothyrium. Relatively fine radial ornament (84 ribs counted at 10 mm growth line on BB 93984, PI. 79, fig. 2), with new costellae arising both by bifurcation and intercalation, the costellae curving round laterally to merge with the hinge line. Growth lines obscure, except anteriorly in old specimens.

Pedicle valve interior. Teeth supported by dental plates extending to the valve floor and diverging at right angles, merging antero-Iaterally with the variably developed muscle-bounding ridges. Thin lanceolate adductor muscle scars between well-impressed anteriorly rounded diductor muscle scars, the whole muscle field bilobed, and extending anteriorly for about one-third of the valve length. Vascular markings obscure.

Brachial valve interior. Cardinal process small, simple (PI. 79, figs. 1,3), becoming stronger and more bulbous in the most gerontic specimens (PI. 78, fig. 9). Pair of stout but relatively short socket plates (the 'supporting plates' of Temple 1965, p. 400) diverging at right angles and attached to the valve floor. Variably developed, poorly defined, thin and low median septum extends for up to one-third of the valve length. Adductor muscle field weakly impressed, but each muscle scar is subcircular and extends anteriorly from between one-quarter and one-third of the valve length.