Parsemileites N. Gen., a New Genus of the Ammonite

Home , Docidoceras, Emileia, Otoites, Otoitidae

Palaeodiversity 1: 167–179; Stuttgart, 30.12.2008. 167

Parsemileites n. gen., a new genus of the ammonite family Otoitidae Ma s c k e from the Lower Bajocian (Middle Jurassic) of Southern England with new information on the Otoitidae from Southern England

Vo l k e r Di e t z e & Ro b e r t B. Ch a n d l e r

Abstract A new Lower Bajocian (Middle Jurassic) ammonite genus Parsemileites n. gen. [M and m] (type-species: Doci doceras liebi Ma u b e u g e ) is erected that represents a separate phyletic strand within the family Otoitidae Ma s c k e , 1907 in the Ovale Zone and the lower Trigonalis Subzone of the Laeviuscula Zone. New information on the evolution of the Otoitidae in Southern England is presented. K e y w o r d s : Parsemileites, Emileia, Otoites, Emileites, sexual dimorphs, evolution, Laeviuscula Zone.

Zusammenfassung Die hier neu aufgestellte Gattung Parsemileites n. gen. [M und m] (Typus-Art: Docidoceras liebi Ma u b e u g e ) stellt einen eigenständigen Entwicklungsstrang innerhalb der Familie Otoitidae Ma s c k e , 1907 in der Ovale-Zone und der unteren Trigonalis-Subzone der Laeviuscula-Zone (Unter-Bajocium, Mittlerer Jura) dar. Neue Erkenntnisse über die Entwicklung der Otoitidae in Südengland werden bekannt gemacht.

Contents 1. Introduction ...... 167 2. A new genus of the family Otoitidae Ma s c k e : Parsemileites n. gen...... 168 Parsemileites n. gen. liebi (Ma u b e u g e , 1955) [M]...... 171 Parsemileites n. gen. cricki (Pa r s o n s , 1977) [m]...... 171 3. Emileia Bu c k m a n , Otoites Ma s c k e , and Emileites Bu c k m a n in Southern England ...... 173 3.1. Emileia Bu c k m a n and Otoites Ma s c k e ...... 173 3.2. Emileites Bu c k m a n ...... 175 4. References...... 176

1. Introduction having been described in 1818 by J. So w e r b y from Southern England. The lectotype of this species is produced here as Southern England is a classic area for researching am- a photograph for the first time (Pl. 1, Fig. 1a–c). monites of the family Otoitidae Ma s c k e , 1907. S. S. Bu c k - The relationship between Emileia and Emileites is of m a n (1909–1930) erected in his (Yorkshire) Type Ammo- particular interest in that these different morphogenera nites (TA) several new taxa included in the family Otoiti- represent either different taxa or a striking example of dae and Pa r s o n s (1977) presented new conclusions on the developmental polymorphism sensu Ma t y j a (1986). The phylogeny of the group. results are of general importance for ammonite classifica- New, precise bed-by-bed collections made over the tion as other examples of parallel ranging ‘micro- and years from most of Bu c k m a n s (1893) classical sites have macromorphs’ have also been identified including: Mol yielded large numbers of otoitid ammonites. We present listephanus and Stephanoceras, Berbericeras and Mor evidence that supports the separation of some of the am- phoceras, Abbasites and Erycites, and within the genus monites formerly included into Emileites into a new genus, Witchellia. The world-wide distribution of the Otoitidae Parsemileites. A more complete interpretation of the phy- makes the family important for correlation between dif- logeny of other members of the family, whose biostratigra- ferent faunal realms. phy is now much better understood, will require further The ammonites collected by the authors have been do- study before the relationships are evaluated. Descriptions nated to the Sedgwick Museum, Cambridge (SM – coll. of other faunas including Docidoceras, Trilobiticeras, RBC, currently in the care of the co-author) and to the Emileia, Emileites and Otoites will follow. The type-species Staatliches Museum für Naturkunde Stuttgart (SMNS – of the genus Emileia Bu c k m a n , 1898 is Ammonites brocchii, coll. VD). 168 p a l a e o d i v e r s i t y 1, 2008

Acknowledgements the Laeviuscula Zone, Lower Bajocian, Middle Jurassic. Sa d k i We thank R. Bö t t c h e r (Stuttgart), W. Et t e r (Basel), A. v. (1996) reports specimens from the central High Atlas of Mo- Hi l l e b r a n d t (Berlin), J. Hu x t a b l e (Taunton), C. Pa r s o n s (Lon- rocco from comparable levels. At Cabo Mondego (Portugal) the don)†, A. Pr i e u r (Lyon), L. St e e l (London), J. Wh i c h e r (York) genus is restricted to the Ovale Zone (Fe r n á n d e z -Ló p e z et al. for valuable help. Special thanks are due to the reviewers A. 1988). Gá l a c z (Budapest) and S. Fe r n á n d e z -Ló p e z (Madrid) and to the R e c o r d s : Southern England (Pa r s o n s 1977, Ch a n d l e r et land owners and tenants: E. Di g b y (Sherborne Castle Estates), J. al. 2006, Di e t z e et al. 2007), Southern France (Do u v i l l é 1884), La r w o o d & H. Po w e l l (Natural England), the Woodland Trust, Spain (Sa n d o v a l 1983), Portugal (Fe r n á n d e z -Ló p e z et al. 1988), Winchester College, B. Lo c k (Sherborne), R. Lo x t o n (Bradford Morocco (Sa d k i 1994), Southern Germany (coll. V. Di e t z e , un- Abbas), R. Hi lli er (Sherborne), D. To l l e y (Stoke Knapp), J. published), ?Iran (Se y e d -Em a m i 1967), ?Tibet (Ar k e l l 1953). Si b l e y (Beaminster) and D. So l e (Axminster). We are indebted to L. St e e l of the Natural History Museum, London for organis- D i a g n o s i s . – Extremely small ammonites. Adult ing photographs of specimens in the collections. We thank the macroconchs attain diameters of ~50 mm maximum, adult Wessex Cephalopod Club in particular J. Ca l l o m o n (London), microconchs of ~28 mm maximum. Inner whorls of both A. En g l a n d (London) and M. Hi g g i n s (Mapperton) for assis- tance in the field. are cadiconic with a broad, depressed cross section. The prominent primary ribs persist to the end of the body Abbreviations chamber and are terminated by small spines or tubercles. * type specimen The dense secondary ribs, about three to five per primary, Aa Aalenian start at the broadest part of the shell and cross the venter Bcº body chamber length in degrees uninterruption. The bodychamber is about 75 % to 100 % Bj Bajocian D preserved diameter of specimen (mm) of the last whorl. HT holotype Comparisons with related taxa. – Macro- [M] macroconch ammonite species conch Parsemileites n. gen., Emileites and the circum-Pa- [m] microconch ammonite species cific Pseudotoites are closely related. The difference is the Pn number of primary ribs on last preserved whorl Ud umbilical diameter (mm) much smaller adult size of complete adult Parsemileites Wb whorl breadth at the end of preserved specimen (mm) n. gen. compared to adult and complete Emileites and Wh whorl height at the end of preserved specimen (mm) Pseudotoites. The holotype of Emileites malenotatus Bu c k m a n (TA Acronyms of repositories 6, pl. 702; Fig. 1a–b), type species of the genus Emileites, BMNH Natural History Museum, London is completely septate to a maximum diameter of 42 mm, GSM Geological Survey Museum, Keyworth, Nottingham SMC Sedgwick Museum, Cambridge this being almost the maximum size of macroconch of SMNS Staatliches Museum für Naturkunde Stuttgart Parsemileites n. gen. with about one whorl of bodychamber (Figs. 1e–f, 3a–p, 4l). Macroconch Parsemileites n. gen. retains a cadiconic morphology to the end of the 2. A new genus of the family Otoitidae Ma s c k e : bodychamber. The whorl section becomes slightly less Parsemileites n. gen. depressed and more circular at the end. Bullae-like tubercles at the lateral edge persist throughout. In contrast Suborder Ammonitina Hy a t t , 1889 Emileites has a more planulate and egreding bodycham- Superfamily Stephanoceratoidea Ne u m a y r , 1875 ber, lacking the bullae-like primaries (Fig. 1c–d, g–h), but Family Otoitidae Ma s c k e , 1907 possessing either short, accentuated, or long persisting primaries. The adult size of complete Emileites can reach Genus Parsemileites n. gen. [M and m] more than double of the adult size of Parsemileites n. gen. (Fig. 1). Ty p e s p e c i e s : Docidoceras liebi Ma u b e u g e , 1955. “Australasian” Pseudotoites (type species Stephano D e r i v a t i o n o f n a m e : To indicate the close resem- ceras leicharti Ne u m a y r , refigured in Sp a t h 1939: pl. 1, blance to Emileites and in memoriam to Co l i n Fr e d r i c k Pa r s o n s (1945–2008) †, highly regarded researcher of ammonites and fig. 1; pl. 2, fig. 4; for examples see Ar k e l l & Pl a y f o r d stratigraphy of the Inferior Oolite. 1954; proposals for a revision see Ha l l 1988) show, with I n c l u d e d s p e c i e s : Docidoceras liebi Ma u b e u g e [M] the exception of larger adult size, a close resemblance to and Trilobiticeras cricki Pa r s o n s [m]. We use in this investiga- Parsemileites n. gen., however the bodychamber of tion the morphospecies concept and keep thus the morphological different micro- and. macroconchs separated. In a biological Parsemileites n. gen. never becomes planulate and evolute sense these sexual dimorphs belong to the same biospecies. The as in some “Australasian” Pseudotoites. The “Andean and dimorphic partnership is based upon both having identical inner Alaskan” Pseudotoites (We s t e r m a n n & Ri c c a r d i 1979, whorls of dimorphs (Fig. 4k, l), extremely small size of adult We s t e r m a n n 1969) show a greater variability ranging specimens of both dimorphs (Fig. 3, 4) and the identical stratigraphical range of both morphospecies. from sub-planulate and evolute to moderately cadiconic S t r a t i g r a p h i c a l r a n g e : In Southern England from and more involute, apparently with all stages of ontogeny the Ovale Zone (Bj-5) to the lower Trigonalis Subzone (Bj-7b) of represented (for details see We s t e r m a n n & Ri c c a r d i 1979: d i e t z e & c h a n d l e r , a n e w g e n u s o f t h e a mm o n i t e f a m i l y o t o i t i d a e 169

Fig. 1. a–b. Emileites malenotatus Bu c k m a n [M], holotype; partly preserved phragmocone of a larger specimen lacking bodychamber. Figured for comparison is c–d (with part of the bodychamber) and g–h (complete to the mouthborder). Probably Ovale Zone, Ovale Bed, Dundry Hill; GSM no. 49293. c–d. Emileites malenotatus Bu c k m a n [M], inner whorls exactly match the holotype of the species; Bed 8 b(ii) of the Ovale Bed (Di e t z e et al. 2007), Dundry Hill, Little Down Wood, Ovale Zone; SM X 40342. e–f. Parse mileites n. gen. liebi (Ma u b e u g e ) [M], holotype; slightly more than ¾ of the last whorl is bodychamber, retaining cadiconic morphology, in comparison to the planulate and egreding bodychamber of Emileites emended; “Couches à sowerbyi; Zone à Sowerbyi”, Sur Soulce sur Envelier (Jura bernois, Switzerland); Musée de Bâle, J 673. g–h. Emileites aff. malenotatus Bu c k m a n [M], complete specimen of the inflated variant; Bed 6 c of the Sandford Lane Fossil Bed, Sandford Lane Quarry (Sherborne), Laeviuscula Zone, Trigonalis Subzone; SMNS 67358. i–m. Parsemileites n. gen. cricki (Pa r s o n s ) [m], holotype; Bed 2 of the Ovale Bed of Barns Batch Spinney (Pa r s o n s 1979), Ovale Zone; BMNH C 79426. – All figures in natural size; ● marks the beginning of the body chamber.

137), but always retaining bullae-like tubercles. The in- ceroides (To r n q u i s t )), but always much bigger than adult nermost whorls are very similar to those of Parsemileites Parsemileites n. gen. n. gen. (Fig. 2c). The oldest “Andean” Pseudotoites from The genus Docidoceras (type species D. cylindroides the Singularis Zone (Ps. singularis (Go t t s c h e ) and Ps. Bu c k m a n ) reaches much larger sizes, with an inflated crassus We s t e r m a n n & Ri c c a r d i ) are smaller compared shell, eccentric body chamber and accentuated primaries to the younger Pseudotoites (Ps. argentinus Ar k e l l , Ps. without bullae-like tubercles. transatlanticus (To r n q u i s t ) (Fig. 2a–b) and Ps. sphaero Pseudocidoceras (type species Pse. widebayense We s - 170 p a l a e o d i v e r s i t y 1, 2008

Fig. 2. a–b. Pseudotoites transatlanticus (To r n q u i s t ) [M], topotype; almost complete specimen; Paso del Espinacito (“Pass”, San Juan Province, Argentina) [together with first Sonninia espinazitensis and latest S. altecostata, still without Chondromileia]; top of Singularis Zone; SMNS 67359 [coll. v. Hi l l e b r a n d t 680106/4]. c. Pseudotoites singularis (Go t t s c h e ) [M], topotype; phragmocone showing the close resemblance to Emileites and Parsemileites n. gen.; Paso del Espinacito (“Grat”, San Juan Province, Argentina) [specimen cited in We s t e r m a n n & Ri c c a r d i 1979: 140; just above bed with Fissilobiceras zitteli, S. crassispinata and Pseudotoites sp. [m] and below bed with Pseudotoites sphaeroceroides and S. altecostata]; Singularis Zone; SMNS 67360 [coll. v. Hi l l e b r a n d t 680107/2–3]. – All figures in natural size; ● marks the beginning of the body chamber.

t e r m a n n ) is intermediate between Docidoceras and rapid contraction of the body chamber (Pa r s o n s 1977: Pseudotoites. The genus reaches a much larger adult size 108). In contrast Trilobiticeras (type species T. trilobi compared to Parsemileites n. gen., which has a longer toides Bu c k m a n ) shows coronate inner whorls, a depressed stage with prominent primary ribbing and a coronate body chamber and small spines or tubercles at the dividing bodychamber. point of the primaries. The oldest Otoites (type-species Frogdenites (type species Frogdenites spiniger Bu c k - Ammonites sauzei d’Or b i g n y ), O. douvillei Pa r s o n s from m a n ) occurs in the top of the Laeviuscula Zone. The genus the Ovale Zone, has a slightly larger size and coarser rib- shows small spines at the dorso-lateral edge, missing in bing compared to microconch Parsemileites n. gen. A Parsemileites n. gen. Frogdenites was considered by Pa r - characteristic feature of Otoites and Emileia are the “club”- s o n s (1977, text-fig. 3) to be an offshoot of “Trilobiticeras shaped primary ribs, terminated by blunt nodes, from cricki”. which arise two or more rounded secondary ribs (Pa r s o n s The microconchs of Parsemileites n. gen. are much 1977: 102; Pl. 1, Fig. 1–2). smaller than the macroconchs. The size ratio of micro- These differences make it necessary to separate the conchs (P. cricki) to macrocochns (P. liebi) is with 1 : 2 new genus Parsemileites within the family Otoitidae. extremely low. P. cricki shows cadiconic inner whorls and C o m m e n t s . – The separate branches Emileia [M] – d i e t z e & c h a n d l e r , a n e w g e n u s o f t h e a mm o n i t e f a m i l y o t o i t i d a e 171

Otoites [m], Pseudotoites [M and m], Pseudocidoceras [M ending in small tubercles or spines. From the point of divi- and m] and Parsemileites n. gen. [M and m] appear to sion two to five secondaries cross the venter without inter- share a common root in a Tethyan ancestor. Emileites [M] ruption. Some secondaries start between the tubercles or is either a micromorph of Emileia [M] or a genus running spines. parallel with it through time, unrelated but able to mimic C o m m e n t s . – In Southern England the species oc- its evolutionary progress in a way we are as yet unable to curs only at three sites to date: It is abundant in the Ovale understand. The Pacific Chondromileia [M and m], itself Zone (Bj-5/Bj-6b) of Dundry Hill and rare at the Ovale an offshoot of Emileia – Otoites, is a link between Otoiti- Zone/Trigonalis Subzone boundary at Sandford Lane and dae and Sphaeroceratidae. Bruton Railway Cutting (Br-LC). The bulk of specimens from Southern England are less broad and less coronate (Fig. 3a–p) compared to the holotype (Fig. 1e–f), but are Parsemileites n. gen. liebi (Ma u b e u g e , 1955) [M] included in the extreme of the variability range (Fig. 3a– Figs. 1e–f, 3a–p, 4l p). With the restricted stratigraphical range and overlap- ping variability observed in English specimens with the v pars 1950 Docidoceras n. sp. – Ma u b e u g e & Li e b , p. 448. holotype we regard all as conspecific belonging to one v pars * 1955 Docidoceras liebi n. sp. – Ma u b e u g e , p. 42, pl. 9, species, P. liebi. The modification of the body chamber fig. 1 [holotype], non pl. 9, fig. 2 [= phragmocone (more compressed than the phragmocone) and comparable of Emileites sp.]. sizes of complete specimens point to the specimens being v non 1968 Docidoceras cf. liebi Ma u b e u g e . – Ba y e r , p. 1, pl. 1 [= Emileites sp.]. adult (Ca l l o m o n 1988). It has not been possible to observe 1974 Emileites (Emileites) liebi (Ma u b e u g e ), M. – Pa r - approximation of the last suture lines in our material as we s o n s , pp. 168, 169. have not been able to find a specimen of the size 1977 T. (Emileites) malenotatus (S. Bu c k m a n ). – Pa r - (d = 50.5 mm) figured by Pa r s o n s (1977, pl. 17, fig. 10). s o n s , p. 105, pl. 17, fig. 10. 1979 Trilobiticeras (Emileites) liebi (Ma u b e u g e ). – Pa r - Measurements (mm) s o n s , p. 144, pl. 2, figs. 4, 5. 1983 E. (Emileia) malenotata Bu c k m a n . – Sa n d o v a l , Specimen Figure D Ud Wb Wh Pn Bcº p. 182, pl. 6, fig. 3. Holotype 1e–f 42 13 25 16 pars 1985 Emileites malenotatus Bu c k m a n . – Fe r n á n d e z - 26 ~320 Ló p e z , p. 345, pl. 37, figs. 4, 6, non 2. SMC X40083 3c–d 41 12 27 16 26 ~330 1988 Emileites malenotatus Bu c k m a n . – Fe r n á n d e z - SMC X40154 3a–b 41 12 22 18 ~22 ~300 Ló p e z et al., p. 308, fig. 2, pl. 1, fig. 6. v pars 1990 Docidoceras (Emileites) aff. malenotatum [M]. – SMC X40345 3g–h 39 15 21 15 ~23 ~320 Ca l l o m o n & Ch a n d l e r , p. 97. SMNS 67356 3k 33 10 20 15 ~23 ~330 1990 Docidoceras (Emileites) liebi Ma u b e u g e . – Ca l l - SMNS 67357 3p 29 11 ? 13 ? ~230 o m o n & Ch a n d l e r , p. 97. SMC X40176 3l–m 29 9 19 13 pars 1996 Emileites malenotatus Bu c k m a n . – Sa d k i , pp. 138, ~21 ~360 139, 185, pl. 8, fig. 2. SMC X40175 3n–o 29 8 18 13 ~25 ~70 1996 Emileites liebi (Ma u b .). – Sa d k i , p. 139. SMC X40346 3e–f 26 9 16 11 ~26 ~270 v 2006 Emileites malenotatus Bu c k m a n . – Ch a n d l e r et al., p. 349. v 2007 Docidoceras” [gen. nov.] liebi Ma u b e u g e [M]. – Di e t z e et al., p. 18, pl. 9, figs. 3–5. Parsemileites n. gen. cricki (Pa r s o n s , 1977) [m] H o l o t y p e : Ma u b e u g e (1955, p. 42, pl. 9, fig. 1), Musée de Figs. 1i–m, 4a–k Bâle, J 673, cast re-figured here as Fig. 1e–f. [Ma u b e u g e ’s figured paratype (pl. 9, fig. 2) is a phragmocone lacking bodychamber and thus inner whorls of an Emileites (emend.)]. 1974 E. (Trilobiticeras) sp. nov., m. – Pa r s o n s , p. 168, Ty p e l o c a l i t y : Sur Soulce sur Envelier, Jura bernois, 169. Switzerland. * 1977 Trilobiticeras (Trilobiticeras) cricki sp. nov. (m.). Ty p e h o r i z o n : “couches à sowerbyi; Zone à Sowerbyi” – Pa r s o n s , p. 106, pl. 17, figs. 1 [holotype], 2–3, 5 (intercalated between Zone à laeviuscula and Zone à discites [with synonymy]. (Ma u b e u g e & Li e b 1950, Ma u b e u g e 1955). In modern interpre- 1979 Trilobiticeras (T.) cricki Pa r s o n s . – Pa r s o n s , tation: Ovale Zone or Trigonalis Subzone of the Laeviuscula pp. 141, 144, 145. Zone. 1985 Trilobiticeras cricki Pa r s o n s . – Fe r n á n d e z -Ló p e z , S t u d i e d m a t e r i a l : 24 specimens. p. 356, pl. 37, fig. 3. 1988 “Trilobiticeras” cricki Pa r s o n s . – Fe r n á n d e z -Ló- D i a g n o s i s a n d d e s c r i p t i o n . – The small spe- p e z et al., fig. 2, p. 308. cies reaches a max. size of ~50 mm. The phragmocone is 1990 Docidoceras (Trilobiticeras) cricki Pa r s o n s [m]. cadiconic. The bodychamber – about 75 % to 100 % of the – Ca l l o m o n & Ch a n d l e r , p. 97. non 1996 “Trilobiticeras” cricki Pa r s o n s . – Fe r n á n d e z -Ló- last whorl – shows a slight uncoiling of the umbilical seam p e z et al., fig. 4, pl. 1, fig. 1 [= Otoites ex gr. douvil with some compression of the whorl section. The prima- lei Pa r s o n s ). ries, remaining prominent to the smooth persistome and 1996 T. cricki Pa r s . – Sa d k i , pp. 138, 139. 172 p a l a e o d i v e r s i t y 1, 2008

Fig. 3. Parsemileites n. gen. liebi (Ma u b e u g e ) [M]. – a–j. Ovale bed, Ovale Zone. a–b. Dundry South Main Road Quarry, bed 2; SM X40154. c–d. Specimen close to the holotype of P. liebi; Dundry South Main Road Quarry, bed 8a; SM X40083. e–f. Juvenile specimen; Dundry Little Down Wood, bed 8 a; SM X40346. g–h. Dundry Little Down Wood, bed 8 b(i); SM X40345. i–j. Dundry Little Down Wood, bed 8 b(i); SM X40344. – k–p. Lowermost Trigonalis Subzone, Laeviuscula Zone. k. Sandford Lane Quarry (Sherborne), boundary bed 6 c/d; SMNS 67356. l–m. Bruton Lusty Railway cutting, bed 7; SM X40176. n–o. Bruton Lusty Railway cutting, bed 7b; SM X40175. p. P. liebi (left) and Bradfordia sp., Sandford Lane Quarry (Sherborne), lower part of bed 6 c; SMNS 67357. – All figures in natural size; ● marks the beginning of the body chamber.

v 2006 Otoites or Trilobiticeras cricki Pa r s o n s . – Ch a n - S t u d i e d m a t e r i a l : 27 specimens. d l e r et al., p. 349, pl. 6, fig. 4. v 2006 Otoites or Trilobiticeras douvillei Pa r s o n s . – D i a g n o s i s a n d d e s c r i p t o n . – See Pa r s o n s Ch a n d l e r et al., p. 349, pl. 7, fig. 4. v 2007 “Trilobiticeras” [gen. nov.] cricki Pa r s o n s [m]. – (1977: 106). Small sized microconchs with coronate inner Di e t z e et al., p. 18, pl. 9, figs. 6–8. whorls. Sharp primary ribs, terminated by small tubercles H o l o t y p e : Pa r s o n s (1977: 106, pl. 17, fig. 1), BMNH or spines, fading into 3 to 5 secondary ribs, which cross C 79426, re-figured here as Fig. 1i–m. the venter without interruption. Body chamber – about Ty p e l o c a l i t y : Barns Batch Spinney, Dundry Hill, 75 % to 100 % of the last whorl – shows an uncoiling of Southern England. Ty p e h o r i z o n : Ovale-bed; Ovale Zone, faunal horizon the umbilical seam and a coarsening of the tubercles and of Witchellia romanoides (Bj-5) or Shirbuirnia gingensis (Bj- secondaries. The primary ribs fade on the body chamber 6b). and the aperture posses two spatulate lappets. d i e t z e & c h a n d l e r , a n e w g e n u s o f t h e a mm o n i t e f a m i l y o t o i t i d a e 173

Fig. 4. a–k. Parsemileites n. gen. cricki Pa r s o n s [m]. – a–b. Dundry Little Down Wood, bed 8 b(ii), Ovale Zone; SM X40348; c–d. Dundry Little Down Wood, bed 8 b(ii), Ovale Zone; SM X40349. e–f. Small variant; Dundry Little Down Wood, bed 8 a, Ovale Zone; SM X40347. g–h. Sandford Lane Quarry (Sherborne), bed 6 c, Trigonalis Subzone of the Laeviuscula Zone; SM X40433. i–j. Bruton Lusty Railway Cutting, bed 7b, Trigonalis Subzone of the Laeviuscula Zone; SM X40179. k. Specimen showing the phragmocone to demonstrate the close resemblance to its macroconch dimorphic partner (Fig. 1l); Dundry Little Down Wood, bed 8a, Ovale Zone; SMNS 67361. – l. Parsemileites n. gen. liebi (Ma u b e u g e ) [M], phragmocone; Dundry Little Down Wood, bed 8a, Ovale Zone; SMNS 67362. – All figures in natural size; ● marks the beginning of the body chamber.

Measurements (mm) 3.1. Emileia Bu c k m a n and Otoites Ma s c k e

Specimen Figure D Ud Wb Wh Pn Bcº D i s c i t e s Z o n e : Docidoceras cylindroides Bu c k - Holotype 1i–m 28 10 14 10 17 ~270 m a n from the Discites Zone of Southern England is almost SM X40348 4a–b 28 11 12 11 18 ~320 certainly the ancestor of the inflated morphs of the genus SM X40433 4g–h 28 11 12 10 18 ~340 Emileia. The occurrence of D. cylindroides in England is SM X40179 4i–j 24 9 10 10 19 ~330 affected by limited exposure of strata of suitable age and SM X40349 4c–d 23 9 11 8 17 ~270 the relative uncommon occurrence of the species itself SM X40347 4e–f 22 8 10 7 19 ~260 apart from a very sporadic occurring bed of late Discites or early Ovale Zone age. It occurs as an extreme rarity already in the faunal horizon Bj-2b (Ch a n d l e r & So l e 1995). Despite decades of intensive collecting in the Dis- 3. Emileia Bu c k m a n , Otoites Ma s c k e , and Emileites cites Zone of Dorset and Somerset no older example has Bu c k m a n in Southern England been found. D. cylindroides is probably an immigrant ar- riving in Southern England in the late Discites Zone. Most A revision of the dimorphic pair Emileia Bu c k m a n , species included in Docidoceras by Bu c k m a n , with the 1898 [M] and Otoites Ma s c k e , 1907 [m], including the exception of D. biforme Bu c k m a n belong to other taxa. taxon Emileites Bu c k m a n , 1922, from Southern England is “D.” perfectum Bu c k m a n is an early stephanoceratid from in progress. The evolution and phylogeny of this group is the Upper Aalenian (Di e t z e et al. 2001) as is “D.” planula complex possibly involving immigration events and local tum Bu c k m a n from the Discites Zone, a micromorph to evolution. In some horizons planulate and inflated morphs the Mollistephanus group (Ch a n d l e r & Di e t z e 2004). coexist (e. g. late Trigonalis Subzone). In contrast, in the Emileia and Otoites have not been found to date in the late Laeviuscula Subzone a population of almost exclu- Discites Zone of Southern England. sively inflated forms occur, with an abrupt change planu- O v a l e Z o n e : The genera Emileia and Otoites are late specimens dominating in the lower Sauzei Zone. Al- very rare elements in the Ovale Zone of Southern England though we recognise slight non sequences in the succes- where the oldest specimens of the genus Emileia are from sion, the time difference is probably too little for local the post-discites beds (Bj-4) of the Ovale Zone (Fig. 5). An evolution to produce such radically different morphology ammonite from the Bu c k m a n collection (BMNH C 78579) and postulate that a migratory influx is the more probable is very evolute and shows a planulate character unlike D. cause. cylindroides Bu c k m a n and unlikely to be directly related 174 p a l a e o d i v e r s i t y 1, 2008

Ammonite Faunal horizons Zone Subzone

Bj-12 Stephanoceras rhytum ? Bj-11b Nannina evoluta

Sauzei Bj-11a Stephanoceras kalum Emileites [M]

Bj-10b Sonninia micracanthica

Bj-10a Witchellia spinifera ?

Laeviuscula Bj-9 Witchellia rubra [m]

Otoites

Laeviuscula Bj-8b Shirbuirnia trigonalis

Bj-8a Sonninia nodatipingue [M] and Trigonalis Bj-7b Witchellia pseudoromanoides

Emileia

[M] Bj-7a Witchellia gelasina

[M and m] Bj-6c Witchellia pseudoromani MS Emileites Bj-6b Shirbuirnia gingensis Ovale Parsemileites Bj-5 Witchellia romanoides

Bj-4 Bradfordia inclusa

Bj-3 Hyperlioceras subsectum

Bj-2b Hyperlioceras rudidiscites

Discites Bj-2a Hyperlioceras walkeri

Bj-1 Hyperlioceras politum

Fig. 5. Stratigraphical range of Emileites [M], Emileia [M] and Otoites [m] and Parsemileites n. gen. [M and m] in the Lower Bajo- cian of Southern England (modified from Di e t z e et al. 2007). d i e t z e & c h a n d l e r , a n e w g e n u s o f t h e a mm o n i t e f a m i l y o t o i t i d a e 175 to it. Slightly younger specimens come from Bj-5/Bj-6b sistent differences. In both genera there is a trend towards (see Di e t z e et al. 2007) with macroconchs (e. g. E. tran larger adult size through time with complete adult speci- siens (Br e m e r ), E. aff. dundriensis Ca l l o m o n et al.) inter- mens of Emileites and Emileia differing by their signifi- mediate to larger and relatively evolute forms. The micro- cant size difference. There is a degree of overlap between conchs have similarity to younger morphologies such as the size ranges of both genera but it is not clear if they O. tumulosus We s t e r m a n n . Some are small, evolute and represent a homogeneous population at any one level. The resemble microconch Parsemileites n. gen. (O. douvillei position is least clear in the Sauzei Zone where the small- Pa r s o n s ). The macroconch E. subcadiconica Bu c k m a n est Emileia and the largest Emileites overlap. In the Ovale probably comes from the Ovale Zone of Dundry, however and lower Laeviuscula Zones Emileites shows a tendency an interpretation of this taxon is difficult as the type towards a more prorsiradiate ribbing style while Emileia specimen is extremely small. has more radial ribbing (see Pl. 1, Fig. 1–2). The inner L a e v i u s c u l a Z o n e : In the upper part of the Tri whorls of both genera are different at identical diameters. gonalis Subzone (Laeviuscula Zone) the genus Emileia Emileia sometimes has blunt nodes or tubercles on the in- becomes more common. Specimens are middle sized and ner whorls, a feature not seen so far in Emileites which show great variability, from planulate to inflated. Part of also shows a strong shift towards more compressed outer the assemblage has an inflated character with shorter ac- whorls and very evolute morphology. The bodychamber is centuated primaries; others occur with more planulate always lightly ornamented terminating with a shallow shells and long primaries (E. contrahens Bu c k m a n and E. constriction and a delicate raised collar, preceding a ven- dundriensis Ca l l o m o n & Ch a n d l e r ; see Ch a n d l e r et al. trally projected simple opening. Emileia always has a 2006 for nominal species of this population). The Laevius- much greater morphological variability within a popula- cula Subzone contains also some large, very inflated spec- tion, with involute spherical forms with strong ornament imens (Sc h w e i g e r t et al. 2006; Pl. 1, Fig. 2a–b), close to E. intergrading with planulate compressed varieties. Emile brocchii (So w e r b y ) (Pl. 1, Fig. 1a–c), type-species of the ites is absent in the Laeviuscula Subzone while Emileia genus Emileia, whose type horizon lies near the boundary remains common. For the present we prefer to retain two of the Laeviuscula and Sauzei zones. Smaller more planu- separate morphogenera, but acknowledge that there is a late morphs occur, but as rarities. Once again the micro- close morphological, possibly biological connection be- conchs have a similar variability to the macroconchs. tween both groups. S a u z e i Z o n e : Emileia and Otoites are very com- One possible explanation for these observations is that mon elements in the Sauzei Zone (faunal horizon of Ste of developmental polymorphism or progenesis (Ma t y j a phanoceras kalum (Bj-11a)) of Southern England. The 1986, Ca l l o m o n 1988), but without firm evidence further macroconchs attain their largest size but retain a high de- comment is impossible. The co-existence of miniature gree of variation of size (~15 cm to maximum ~40 cm). ammonites alongside significantly larger shells of other- The genus shows a rather homogeneous character with wise similar morphology is well known in the Middle Ju- predominantly evolute, planulate shells with long prima- rassic, e. g. Erycites and Abbasites or Stephanoceras and ries (Ch a n d l e r & Di e t z e 2001) centred on E. vagabunda Mollistephanus (Ch a n d l e r & Di e t z e 2004). In almost all Bu c k m a n , E. bulligera Bu c k m a n and E. greppini cases the small shells can be shown to be adult macro- Ma u b e u g e . A typical microconch is Otoites contractus conchs with approximated final sutures, eccentric coiling (So w e r b y ) (Pl. 1, Fig. 3). Rare inflated specimens stand of the body chamber and modified peristome. apart e. g. E. ex gr. schassmanni Ma u b e u g e with long pri- An explanation by Mi g n o t et al. (1993) of niche poly- maries. We have also collected rare specimens of small morphism for the occurrence of small adult individuals involute, almost spherical forms strongly resembling pa- (“dwarfism”) in a population of Toarcian hildoceratids cific Chondromileia We s t e r m a n n & Ri c c a r d i . The taxo- from Italy and North Africa resulting from restricted envi- nomic status of these specimens needs further consider- ronmental conditions (at the bottom of small basins) is not ation. plausible here. Emileia and Emileites coexist through time and parallel changes in morphology. They appear to show equal ability to survive in identical environmental condi- 3.2. Emileites Bu c k m a n tions. On the basis of their microconch dimorphs alone mi- The holotype of the type species of Emileites, E. male croconch Emileites and the microconch genus Otoites are notatus Bu c k m a n (Fig. 1a–b), is a phragmocone of a large inseparable. The known stratigraphic range of Emileites is specimen, which is significantly larger than the Parsemil from the Ovale Zone (Bj-5) to the Sauzei Zone (Bj-11a) eites n. gen. assemblage (see chapter 2, Fig. 1a–h). (Fig. 5). The relation between Emileites and Emileia is not clear. Ovale Zone: ?Emileites ex gr. biforme from the Emileites resembles a micromorphic Emileia but with per- lowest Ovale Zone (Bj-4) of Stoke Knap and the lower 176 p a l a e o d i v e r s i t y 1, 2008

Ovale Zone of Bruton (coll. RBC) are the earliest mem- Ch a n d l e r , R. B. & So l e , D. (1995): The Inferior Oolite at East bers of the genus. The Stoke Knap specimens occur in the Hill Quarry, Bradford Abbas, Dorset. – Proceedings of the Dorset Natural History and Archaeological Society, 117: same horizon (Bj-4) as the oldest Emileia. In slightly 101–108. younger strata (from Bj-5 upwards) typical Emileites male Ch a n d l e r , R. B., Ca l l o m o n , J. H., Ki n g , A., Je ff r e y s , K., Va r a h , notatus rarely occur with typical specimens from Dundry M. & Be n t l e y , A. (2006): The stratigraphy of the Inferior Hill, Bruton and Sandford Lane Quarry. Oolite at South Main Road Quarry, Dundry, Avon. – Pro- L a e v i u s c u l a Z o n e : Emileites catamorphus ceedings of the Geologists’ Association, 117: 345–375. Di e t z e , V., Ch a n d l e r , R. B., Sc h w e i g e r t , G. & Au e r , W. (2001): (Bu c k m a n ) is an extreme planulate variant within the New stephanoceratids (Ammonitina) from the Lower Bajo- chronocline in which all intermediates from planulate to cian of Bruton (Somerset, S England) and Achdorf (Wutach inflated (Fig. 1g–h) specimens exist. As a morphogenus area, SW Germany). – Stuttgarter Beiträge zur Naturkunde, the acme lays in the Trigonalis Subzone, but specimens Serie B, 312: 1–21. Di e t z e , V., Ch a n d l e r , R. B. & Ca l l o m o n , J. H. (2007): The are lacking in the Laeviuscula Subzone. Ovale Zone (Lower Bajocian, Middle Jurassic) at Little S a u z e i Z o n e : Emileites is rare in the Sauzei Zone Down Wood (Dundry Hill, Somerset, SW England). – Stutt and includes the nominal species Emileites multifidus garter Beiträge zur Naturkunde, Serie B, 368: 1–45. (Bu c k m a n ) and Emileites polymerus (Wa a g e n ) sensu Ga u - Do u v i l l é , H. (1884): Sur quelques fossiles de la zone à Amm. 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Addresses of the authors: Vo l k e r Di e t z e , Benzstraße 9, 73469 Riesbürg, Germany E-mail: [email protected] Ro b e r t B. Ch a n d l e r , Shirley High School, Shirley Church Road, Croydon, Surrey CRO 5EF, UK E-mail: [email protected]

Manuscript received: 30.6.2008, accepted: 5.11.2008. 178 p a l a e o d i v e r s i t y 1, 2008

Plate 1

Fig. 1a–c. Emileia brocchii (So w e r b y ) [M], lectotype; from “Sherborne, Dorset”; by matrix it comes from a locality in the Sandford Lane area; probably Laeviuscula Subzone of the Laeviuscula Zone; BMNH 43906a.

Fig. 2a–b. Emileia cf. brocchii (So w e r b y ) [M], part of the phragmocone showing the characteristic features of the genus; Frogden Quarry (Oborne near Sherborne), bed 3, Laeviuscula Subzone of the Laeviuscula Zone; SMNS 67363.

Fig. 3. Otoites contractus [m] (So w e r b y ); Sandford Lane Quarry (Sherborne), bed 6 b. Sauzei Zone; SMNS 67364.

All figures in natural size; ● marks the beginning of the body chamber. d i e t z e & c h a n d l e r , a n e w g e n u s o f t h e a m m o n i t e f a m i l y o t o i t i d a e 179