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Earth Science Frontiers, Vol. 17, Special Issue, Aug. 2010 ISSN 1005-2321 204 The Eligminae, Symbiotic Oysters of the Middle Jurassic N.J. Morris, R.C. Cleevely, D. Clements Natural History Museum, Cromwell Road, London SW7 5BD, UK (E-mail: nichola.morris@nhm.ac.uk) The Eligminae are preserved in limestone platform facies of the Middle Jurassic. Initially they were recognized in the Bathonian of Northern france and southern Poland, then in the Bathonian and Callovian of more southerly parts of France. Their oyster-like morphology, but lack of any conspicuous area of ce- mentation, has convinced palaeontologists from Eudes- Deslongchamps onwards that they lived symbiotically within soft-bodied organisms, comparable to soft- bodied sponges of the class Demospongiae. The extant bivalve genus Vulsella and the oyster Cryptostrea permollis (G.B. Sowerby !!) live in this manner today. The detailed morphology and shell structure associate the Eligminae with the oysters rather than Vulsella. The shell is calcitic except apparently except for the muscle scars and the surface of the ligament area. We have found no evidence of an outer shell layer of prismatic calcitewhich occurs in at least some Gry- phaeidae. The outer shell layeris formed of cross-foliated calcitein common with other Jurassic ribbed or plicate oysters. The inner shell layer consists of thin folia of calcite with hollow interspaces, infilling the shell but retaining its relatively light weight. This in some species gives a blistered appearance to the inner surface of the shell. In our well preserved material we have found no evidence which Douville considered that he had observed and led him to link Eligmus taxonomically with Vulsella. Although we now know that such a nacreous inner layer occurs in several Triassic oysters. The ribbing pattern of the earliest species, Eligmus integer, from the Late Bajocian, is practically identical to that of typical Actinostreon, to which we consider it is most closely related. Although there is little evidence of any cementa- tion in early growth stages the initial growth produced backward pointing umbones, typical only of the oysters and the Inoceramidae. Vulsella on the other hand, beneath a thick and scaley peristracum, has an outer shell layer of prismatic calcite and an inner layer of nacreous aragonite; a combination which is normally considered to be a more primitive shell structure combination within the Pteriomorpha. Oyster-like chomata are presenting “Eligmus” aualites and Gryphaelegmus but have not been observed in Eligmus sensu stricto. Apart from the notable exception of Gryphae- ligmus, the early growth stages are sometimes inaequi- valved, with a more convex left valve but approach a more equivalved condition in later life. Most species have a noticeable gape between the posterior of the hinge and the Branchytellum. In most species this is in the form of a slightly curved shell margin but in Eligmus polytypus the margins are in the form of irregular sinusoidal curves which form an extensive irregular gape. The form and position of these posterior “dorsal” gapes is consistant with ease of rejection of waste particles from the mantle cavity in a position with the normal ventral margin pointing upwards as occurs in living Vulsella and the giant clams. The group is widespread across the Middle East during the Middle Jurassic and in spite of the difficulty of dating the rocks in which they occur. They seem to have originated from an ancestor resembling Actino- streon in the Late Bajocian, evolved into at least five species in the Bathonian, and with at least three distinct species remaining towards the end of the Callovian. By re-examining the morphology of this group we suggest the possibility that the different contem- poraneous species occurred within different host species as is understood for living Vulsella. The group apparently became extinct at the end of the Callovian, possibly reflecting the demise of their host species. We consider that the comparable symbioses of oysters have happened on at least three separate occa- sions since Jurassic times. Key words: Jurassic Symbiotic Oysters; Faunal Change References: Douvillé H. Etudes sur Lamellebranchs. Vulsellidés. Annales de Paléontologie, 1907, 2: 97-118, pls 15-16. Paris. Eudes Deslongchamps J. Descriptiond’un nouvelle genre de coquilles b bivalves fossils, Eligmus. Mém. Soc. Linn, Normand, 1856, 10: 272-293, pls 15-16. Hertlein L. G., Cox L.R. Treatise on Invertebrate Paleonology. Geological Society of America and University of Kansas Press, 1969: 326-332.
Earth Science Frontiers, Vol. 17, Special Issue, Aug. 2010 ISSN 1005-2321 The Early to Middle Jurassic Flora from Primorye Region (Russian Far East) E.B. Volynets¹, S.A. Shorokhova² 1. Institute of Biology and Soil Science, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690022, Russia (E-mail: volynets@ibss.dvo.ru, volynets61@mail.ru) 2. Institute of Engineering and Social Ecology, Far Eastern State Technical University, Vladivostok 690091, Russia (E-mail: shorokhova@mail.ru) The Early and Middle Jurassic floras are known from Partizansk and Razdol’naya Rivers Basins in South Primorye (Krassilov and Shorokhova, 1975; Volynets, 1999, 2008). The Early Jurassic flora (the Hettangian) is collected from the Shitukhe Formation. This flora includes 39 taxa. The Shitukhe floral assemblage consists of horsetails (Equisetum, Neocalamites), ferns (Cladophlebis, Marrattiopsis, Phlebopteris, Clathro- pteris, Hausmannia, and Todites), caytonialeans (Sagenopteris), cycadophytes (Pterophyllum, Ctenis, Nilssonia, and Taeniopteris), conifers (Podozamites, Cycadocarpidium, Pityophyllum, and Elatocladus), ginkgoaleans (Ginkgoites, Baiera, and Sphenobaiera), czekanowskialeans (Czekanowskia and Phoenicopsis) and plants of unclear affinity (Linguifolium, Car- polithes). Ferns are dominants, and they are accompanied by cycadophytes and conifers. Cladophlebis (5 taxa) are most diverse among ferns; C. ex gr. haiburnensis (L. et H.) Brong., C. ex gr. denticulata (Brong.) Font. and Cladophlebis sp. are common; C. scoresbiensis Harris is rare. Marratiopsis hoerensis (Schimp.) Thomas and Phlebopteris angustiloba (Presl) Hirm. et Hoerham. are abundant; Cla- thropteris elegans Oishi, Hausmannia sp., Todites sp. are single. Pterophyllum cf. subaequale Harts, Ctenis sulcicaulis (Phill.) Ward and Nilssonia acuminata (Presl) Goeppert are abundant among cycadophytes; Taenio- pteris lanceolata Oishi is typical; Ctenis cf. yokoyamae Krysht., Nilssonia spinosa Krassil. and Taeniopteris sp. are rare. Pityophyllum ex gr. nordenskioldii Heer is abundant among conifers; and Podozamites is most diverse (P. schenkii Heer, P. latifolius (Schenk) Krysht. et Pryn., P. lanceolatus (L. et H.) Schenk). Marratiopsis hoerensis (Schimp.) Thomas, Ph- lebopteris angustiloba (Presl) Hirm. et Hoerham., Cladophlebis scoresbiensis Harris, Ctenis sulcicaulis (Phill.) Ward are guide fossil plants for the Lower Jurassic deposits. The plants of Shitukhe assemblage such as Cla- thropteris, Phlebopteris, Marratiopsis evidence about the humid subtropical climate during the Hettangian. The Middle Jurassic (the Bathonian) plant remains have been found in the Ananyevka (Razdol’naya River Basin) and Monakino (Partizansk River Basin) forma- tions. The floral assemblage is represented by 81 taxa (Volynets, 2008): bryophytes (Thallites), horsetails (Equisetum), ferns (Sphenopteris, Cladophlebis, Klukia, Cyathea, Osmundopsis, Phlebopteris, Ruffordia, Dick- sonia, Coniopteris, Onychiopsis, Adiantopteris, and Acrostichopteris), conifers (Podozamites, Araucarites, Cunninghamia, Pityophyllum, Brachyphyllum, Elato- cladus, Coniferites, and Conites), cycadophytes (Oto- zamites, Dictyozamites, Cycadolepis, Anomozamites, Ptilophyllum, Zamites, Nilssonia, and Pseudocenis), pteridosperms (Thinnfeldia), caytonialeans (Caytonia, Sagenopteris), ginkgoaleans (Baiera and Pseudo- torellia), czekanowskialeans (Czekanowskia and Leptostrobus) and plants incertae sedis (Carpolithes, Taurinia, Schizolepis, Machairostrobus, Radicites). Ferns are dominants, and they are accompanied by conifers and cycadophytes. Among ferns diverse Sphenopteris (S. gracilis Oishi, S. cf. mclearnii Bell, S. aff. latiloba Font., S. kiselevae Volynets, S. sp.) and Cladophlebis (C. naitoi Kimura et Ohana, Cladophlebis toyoraensis Oishi, C. cf. argutula (Heer) Font., C. cf. williamsonii (Brongn.) Brongn., C. sp.) occur. Coniopteris bella Harris, Cladophlebis toyoraensis Oishi, C. naitoi Kimura et Ohana, Onychiopsis psilotoides (St. et W.) Ward are common; Acrostihopteris naitoi Kimure et Ohana, Acrostihopteris sp., Phlebopteris sp., Ruffordia sp., Coniopteris hymenophylloides (Brongn.) Sew., Dicksonia sp., Cladophlebis cf. argutula (Heer) Font. are rare; Adiantopteris toyoraensis (Oishi) Vassilevsk., Klukia exilis (Phill.) Racib., Cyathea sp., Osmundopsis cf. prynadae Delle, Sphenopteris kiselevae Volynets are single. Among conifers Podozamites ex gr. lanceolatus (L. et H.) Schimp., P. angustifolius (Eichw.) Heer, Elatocladus subzamioides (Moell.) Tur.-Ket. are most numerous in burials; Elatocladus (2 taxa) is common. Brachyphyllum cf. toyoraensis Takah., Brachyphyllum sp., Conites sp. and Coniferites (C. marchaensis Vachr., Coniferites sp.) are rare; Cunninghamia and Araucar- ites are single. Nilssonia (6 taxa) and Dictyozamites (5 taxa) are most diverse among cycadophytes. Dictyozamites nevolinae Volynets and D. tateiwae Oishi are abundant; D. doludenkoae Volynets is rare; D. cf. reiniformis Kimura et Ohana and Dictyozamites sp. are single. Zamites, Ptilophyllum, Otozamites, Anomozamites, Ps- 205
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