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Discovery of the Jaw Apparatus of the Upper Volgian Ammonite Kachpurites Fulgens (Craspeditidae) A

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Discovery of the Jaw Apparatus of the Upper Volgian Ammonite Kachpurites Fulgens (Craspeditidae) A ISSN 00310301, Paleontological Journal, 2014, Vol. 48, No. 6, pp. 580–586. © Pleiades Publishing, Ltd., 2014. Original Russian Text © A.A. Mironenko, 2014, published in Paleontologicheskii Zhurnal, 2014, No. 6, pp. 12–17. Discovery of the Jaw Apparatus of the Upper Volgian Ammonite Kachpurites fulgens (Craspeditidae) A. A. Mironenko Moscow Society of Naturalists email: [email protected] Received June 5, 2013 Abstract—The jaw apparatus of the genus Kachpurites (Ammonoidea, Craspeditidae), consisting of a pair of aptychi and a beakshaped upper jaw is described and figured for the first time. A new aptychus species Praes triaptychus fulgens sp. nov. is established. Aptychi of this species are elongatedtriangular, weakly ribbed, with a welldeveloped inner organic layer and a considerably thinner, often poorly preserved external calcite layer. Specimens of the type series were found in the body chamber of ammonites Kachpurites fulgens (Trautschold), from the Upper Jurassic (Upper Volgian) Kachpurites fulgens Zone of Moscow and the Moscow Region. Keywords: Ammonoidea, Craspeditidae, aptychi, jaw apparatus, Upper Volgian, Russia DOI: 10.1134/S0031030114060100 INTRODUCTION chamber, originally identified as Craspedites okensis Aptychi are jaw elements of ammonites, rarely (Rogov and Mikhailova, 2006), although it is quite found in the Jurassic of the Russian Platform. Aptychi possible that the ammonite belonged to the genus Laevaptychus associated with the ammonite family Kachpurites (M.A. Rogov, pers. comm.). In the earlier, Aspidoceratidae are an exception to this general rule, Middle Jurassic (Callovian) beds, aptychi Praestriap as they are relatively frequently found in the Upper tychus were found both separately from ammonites Kimmeridgian beds (Vischniakoff, 1875; Hantzpergue (Rogov, 2004a), and in the body chambers of et al., 1998; Rogov, 2002a). Aptychi Laevaptychus have perisphinctids, i.e., aptychi Praestriaptychus koenigi in a thick external calcite layer, which explains their good the body chamber of Proplanulites koenigi (Rogov and state of preservation. Other aptychi are much less Gulyaev, 2003) and Praestriaptychus sp. in the body commonly preserved. Aptychi Praestriaptychus, asso chamber of Elatmites sp. (Mitta and Keupp, 2007). ciated with most ammonites of the superfamily Aptychi were also found in the Lower Callovian and Perisphinctoidea, a particularly rare. These are rela Upper Bathonian, together with the ammonites Kep tively thin aptychi with a weakly developed calcite plerites and Sigaloceras (Mitta, 2009; Nikitin, 1884; layer (Engeser and Keupp, 2002). In aptychi of the Keupp and Mitta, 2013). Upper Jurassic Boreal perisphinctids, this initially thin The upper jaws of Jurassic ammonites from the layer is additionally reduced (Rogov and Mikhailova, Russian Platform have only been described from the 2006). Apparently, it was the thin calcite layer of Lower Callovian (Mitta and Keupp, 2004, 2007; Praestriaptychus that made their occurrences so rare. Keupp and Mitta, 2013). They are found in nodules in The ammonite family Craspeditidae Spath, 1924 association with shells of ammonites of the families was abundantly represented at the Jurassic–Creta Cardioceratidae, Kosmoceratidae, and Perisphinc ceous boundary in the Boreal and Subboreal realms tidae, and also in association with the lower jaw (apty (Mitta, 2010). Despite that, aptychi of ammonites of chi) in the body chamber of ammonites of the genus this family have been only mentioned twice in the lit Kepplerites. No upper jaws have been previously found erature. The first record mentioned aptychi Praestri or described from the Volgian of the Russian Platform. aptychus, belonging to ammonites of the family Cras peditidae, but with no description or illustration (Eng eser and Keupp, 2002). In the second record, the MATERIAL aptychus of a craspeditid ammonite was figured, but Isolated and paired aptychi and an ammonite not properly described (Rogov and Mikhailova, 2006). upper jaw were found in the body chambers of the Ammonite aptychi from the Volgian Stage of the ammonite Kachpurites fulgens (Trautschold) (family Russian Platform were described only twice (Rogov Craspeditidae). Ammonites were collected by the 2004b; Rogov and Mikhailova, 2006). Only in one present authors in 2012 in a quarry of the Ramenskii case was an aptychus found in an ammonite body Enrichment Mining Factory, in the vicinity of the vil 580 DISCOVERY OF THE JAW APPARATUS OF THE UPPER VOLGIAN AMMONITE 581 lage of Eganovo (Ramenki District, Moscow Region), (a) (b) 50 km southeast of Moscow (Fig. 1). The quarry mines Rybinsk Volga Late Jurassic and early Cretaceous sands, while the R. Moscow . Yaroslavl R Upper Volgian clay is exposed by drainage trenches. a Mnevniki Tver kv 2 Dubna os M M Another pair of aptychi was found in the body cham o Volga R. sk v ber of in the summer of the same year in a a K. fulgens R Lyubertsy . small section in Moscow, on the bank of the Moscow Zhukovsky Moscow M 2 o sk River (Karamyshevskaya Embankment) (Fig. 1). This v . a 1 Kolomna R R specimen (no. 116/3) was found and donated by ama a 1 . k teur paleontologist Ruslan Shirokov. Ryazan O village of Eganovo 100 km 10 km Bronnitsy All specimens come from the Kachpurites fulgens Domodedovo Zone of the Upper Volgian Substage and were found in entire and incompletely preserved shells of K. fulgens. Fig. 1. Map showing localities. Explanations: (1) quarry of In most cases, these are shells of microconchs or the Ramenskii Mining Enrichment Factory near the vil young specimens, but one aptychus was found in a lage of Eganovo (Ramenki District of the Moscow Region) (55°32′08.28′′ N; 38°03′10.47′′ E); (2) section on the bank supposed macroconch shell. Due to the absence of of the Moscow River on the Karamyshevskaya Embank terminal aperture modifications in representatives of ment, Moscow (55°46′4.12′′ N; 37°28′4.67′′ E). the family Craspeditidae and incomplete preservation of many shells, the identification needs to be based exclusively on the shell size. cite layer is very thin, fragmentary, and appears to be Specimens studied show variously preserved jaw partly dissolved. Apparently, the upper jaw is preserved apparatuses. For instance, specimen nos. 116/1 and essentially in the life position. The width of the lower 116/5 represented isolated aptychus valves. Specimen jaw is 5.5 mm, whereas the parameters of the aptychus no. 116/1 (Pl. 2, fig. 1) is an aptychus with a wellpre are given in the table below. Specimen no. 116/3 served inner and thin fragmentary outer layer. Except (Pl. 2, fig. 3), is a pair of aptychi with a well preserved a small portion in the central region, the aptychus is outer calcite layer, located in the body chamber of a completely preserved. It is located in the middle part microconch. The ammonite diameter is 26 mm; the of the body chamber of a microconch of K. fulgens. aperture is 9 mm high. The aptychi are tightly con The shell diameter of the ammonite shell is 39 mm, nected to each other, but are partly preserved; the api the aperture is 11.5 mm high, the width is 10 mm. The cal regions are lost, and only the side with the terminal parameters of the aptychus are given below, in the spe angles remains. The aptychi are apparently in the life cies description. The aptychus length almost coincides jaw position. This specimen, unlike all other speci with the apertural height. The aptychus surface pos mens, has a very well preserved calcite layer. Its surface sesses smoothened, but distinct ribs and growth lines, shows smoothened ribbing. The color of the calcite and the external margin is somewhat thickened. The layer of this specimen is considerably lighter than that outer calcite layer is very thin, light brown, preserved of other aptychi described in this paper. Because this as small fragments over most of the surface area of the particular specimen was found separately from all aptychus. Specimen no. 116/5 (Pl. 2, fig. 5) is repre other specimens (in a section on the Karamyshevskaya sented by a large aptychus in a fragment of the body Embankment), the difference in preservation is appar chamber of a ribbed (?) macroconch. The complete ently linked to taphonomic differences. In one case shell diameter is unknown, whereas the length of the (specimen no. 116/4), an incomplete macroconch preserved fragment is 65 mm and the maximum whorl shell in the middle of the body chamber contained height is 16 mm. Singular coarse ribs are preserved on paired aptychi and an upper beakshaped jaw fitted the shell surface on the side opposite of the aptychus. between them. The diameter of the ammonite con The surface of the inner organic layer of the aptychus taining the above jaw fragments, is 27 mm, the aper is weakly ribbed, with noticeable, but low ribs and ture height is 9 mm, and the width is 7 mm. Due to the growth lines. This layer is almost completely pre poor state of preservation the aptychus length cannot served, except a small region near the terminal margin be precisely measured, while the width is about 7 mm of the aptychus. The outer calcite layer of the aptychus and the width of each aptychus is 4 mm. The aptychi is preserved as small areas on the organic layer surface. are separated by the rock matrix filling the body cham Specimens nos. 116/2 and 116/3 represent joined ber one is on the outer side and another is on the aptychi (complete ammonite lower jaws). For inner side. The outer calcite layer of one of the aptychi instance, specimen no. 116/2 (Pl. 2, fig. 4) is repre is completely destroyed, while the inner organic layer sented by paired aptychi occurring in the centre of the is incompletely preserved. The second aptychus is vis body chamber of Kachpurites fulgens. Only a fragment ible from the side of the inner layer, which is largely not of the body chamber 30 cm long is preserved.
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