136 



M.K. HOWARTH 



synonyms. Two other names that are probably also synonyms of P. 

 planicosta are P. perplanicosta (Spath, 1925a: 269; 1926£>, 172, pi. 

 9, fig. 2) and P. precompressum Spath ( 1926b, 173, pi. 9, fig. 5), both 

 from beds 83 or 85 at Charmouth. 



Promicroceras capricornoides (Quenstedt, 1883) 



1883 Ammonites capricornoides Quenstedt: 129, pi. 17, fig. 11 



(from Wtirttemberg, Germany). 

 1926i> Promicroceras capricornoides (Quenstedt); Spath: 172, pi. 



9, fig. 3 (from the Turneri Zone, Charmouth, Dorset). 



Range. Beds 436^446.32, Birchi and basal Obtusum Subzones; 

 39 specimens. 



REMARKS. P. capricornoides is slightly more involute, has a more 

 rapidly increasing whorl height and slightly fewer ribs than P. 

 planicosta. 



Family COELOCERATIDAE Haug, 1910 

 Genus APODEROCERAS Buckman, 1921 



REMARKS. Identification of the horizons from which the Yorkshire 

 type and figured specimens were obtained is especially uncertain in 

 Apoderoceras. The originals of A. subtriangulare and its two syno- 

 nyms (A. hamiltoni and A. spicatum) could have come from any of 

 beds 502, 504-07 509, 520 and 522, all of which contain many large 

 fragments of outer whorls as well as a few more complete specimens 

 like the original of A. 'hamiltoni'. Similarly, the originals of A. 

 aculeatum and its three synonyms (A. decussation, A. mutatum and 

 A. leckenbyi) could have come from any of beds 523-526. 



Apoderoceras subtriangulare (Young & Bird, 1822) 



PI. 5, fig. 8; PI. 6, figs 4, 5 



1 822 Ammonites subtriangularisYoung & Bird: 250. pi. 12, fig. 4. 

 1843 Ammonites hamiltoni Simpson: 27. 

 1843 Ammonites spicatus Simpson: 28. 



1913 Deroceras subtriangulare (Young & Bird); Buckman: pi. 

 71 (holotype, WM927). 



1914 Deroceras spicatum (Simpson); Buckman: pi. 103 

 (holotype, WM 920). 



1924 Apoderoceras hamiltoni (Simpson); Buckman: pls530A,B 



(both are the holotype, WM 165). 

 1992 Apoderoceras sp. indet.; Dommergues & Meister: 232, fig. 



5(6) (from nodules at the middle of bed 50 1 . 1 , Wine Haven). 



Range. Beds 501.1-522.1, Taylori Subzone; 41 specimens. 



Remarks. The lowest examples of Apoderoceras are three speci- 

 mens in bed 501.1. Two are very small cadicones, one large enough 

 to have ventro-lateral tubercles, while the third (PI. 5, fig. 8) is part of 

 one side of a whorl at a whorl height of 35 mm that has obscure radial 

 ribs and striae and pointed ventro-lateral tubercles. It is identical 

 with A. subtriangulare at a similar size, and is important for fixing 

 the base of the Taylori Subzone at this level. 



Large A. subtriangulare up to 350 mm diameter, with large 

 ventro-lateral spines and broad flat venters occur in bed 502 and at 

 many more horizons up to bed 522.1. Most are fragments of outer 

 whorls with nothing to link them to the few inner whorls, but an 

 example in bed 507.1 (CA 4006) has both inner and outer whorls, 

 and proves that small inner whorls like those in PL 6, fig. 5 and the 

 very well-preserved specimen of PL 6, fig. 4 develop into the massive 

 outer whorls with broad flat venters and very large ventro-lateral 



spines that are characteristic of A. subtriangulare. The holotype of A. 

 subtriangulare (Buckman, 1913: pi. 7 1) is a fragment of such a large 

 outer whorl. Of the two Simpson species that are placed in syn- 

 onymy, the holotype of A. spicatum (Buckman, 1914: pi. 103) is a 

 very similar fragment of a large outer whorl, though the broad flat 

 venter is not shown because only one side is preserved, while the 

 holotype of A. hamiltoni (Buckman, 1924: pi. 530) is one of the few 

 specimens that show inner and outer whorls preserved in the same 

 individual. [Note the remarkable resemblance of PL 6, fig. 4 to a 

 depressed-whorled species of the Toarcian genus Peronoceras. eg. P. 

 perarmatum (Young & Bird), Howarth, 1978: pi. 4, fig. 7; the latter 

 differs only in having well-defined ribs on the side of the whorl, 

 compared with the poor, irregular or striate ribs on the inner whorls 

 of Apoderoceras subtriangulare]. 



Apoderoceras aculeatum (Simpson, 1843) 



PI. 6, fig. 2: PI. 7, fig. 1 



71843 Ammonites marshallani Simpson: 24. 



1843 Ammonites decussatus Simpson: 25. 



1843 Ammonites aculeatus Simpson: 27. 



1855 Ammonites mutatus Simpson: 63. 



1876 Aegoceras aculeatum (Simpson); Blake: 278, pi. 7, fig. 4 

 (BMC. 17878). 

 1880/82 Aegoceras leckenbyi Wright: 344 (1882), pi. 30 (1880), 

 figs 1-3 (lectotypeof/ecfcenbv/ (designated Howarth, 1962: 

 109), SM J 18224), figs 4-7 (paralectotype of leckenbyi, 

 also holotype of decussation. SM J 18225). 



1913 Deroceras aculeatum (Simpson); Buckman: pis 72A-C 

 (paratype, WM 177; the holotype is lost). 



1914 Deroceras mutatum (Simpson); Buckman: pi. 105 (holotype, 

 GSM 26406). 



1962 Apoderoceras decussatum (Simpson); Howarth: 109, pi. 

 16, fig 1 (holotype, SM J18225). 

 71962 Apoderoceras marshallani (Simpson); Howarth: 109, pi. 

 15, fig. 5 (holotype. WM 468); the holotype is only 16 mm 

 diameter, and although it could be a very small example of 

 A. aculeatum. Simpson's species is not accurately determin- 

 able. 



Range. Beds 523-526.6, Taylori Subzone; 1 5 specimens. There are 

 also single specimens of Apoderoceras sp. indet. in beds 526.7 and 529. 



Remarks. Specimens from beds 523-526 differ from A. 

 subtriangulare in beds 501-522 in having the outer whorls more 

 rounded, with evenly arched whorl sides and venter, no definite ventro- 

 lateral angle, and smaller ventro-lateral tubercles on the inner whorls. 

 These stratigraphically higher specimens belong to the species A. 

 aculeatum (Simpson), of A. decussatum and A. leckenbyi are synonyms 

 (Ammonites aculeatum and A. decussatum are both of Simpson, 1843, 

 and therefore have equal priority; the name for the species was selected 

 by Blake (1876: 278), who, as 'First Reviser' (ICZN Code, art. 24.2), 

 chose aculeatum as the name for the species). A. marshallani. another 

 Simpson name of the same date ( 1 843), is probably also a synonym, but 

 the holotype is too small to be definitely identifiable, and A. mutatum 

 (Simpson. 1855)andA. leckenbyi (Wright, 1880) are two more syno- 

 nyms, judging from their well-preserved type specimens. 



The specimen figured in PL 7, fig. 1 is a fairly large, wholly septate 

 example of A. aculeatum and PL 6, fig. 2 has well-preserved inner 

 whorls showing much smaller ventro-lateral tubercles than in A. 

 subtriangulare (cf. inner whorls of PL 6, fig. 5). 



Other species of Apoderoceras: 



1. lApoderoceras sinuatum (Simpson, 1855: 62); Buckman, 1914: 



