Journal of Paleontology, 92(2), 2018, p. 157–169 Copyright © 2017, The Paleontological Society 0022-3360/18/0088-0906 doi: 10.1017/jpa.2017.81


A new late Carboniferous coleoid from Oklahoma, USA: implications for the early evolutionary history of the subclass Coleoidea (Cephalopoda)


Larisa A. Doguzhaeva1 and Royal H. Mapes2


1Department of Palaeobiology, Swedish Museumof Natural History, P.O. Box 50007, Stockholm SE-104 05, Sweden ⟨larisa.doguzhaeva@gmail.com⟩ 2American Museum of Natural History, Central Park West at 79th Street, New York City, New York 10024-5100, USA ⟨mapes@ohio.edu⟩


Abstract.—The limited record of the bactritoid-like coleoid cephalopods is here expanded due to discovery of a late Carboniferous (Moscovian) orthocone comprising a phragmocone and a body chamber with a proostracum-like structure, a sheath-like rostrum, an ink sac, and a muscular mantle preserved on top of the conch. The specimen comes from the Wewoka Formation in the vicinity of the city of Okmulgee, Oklahoma, which previously yielded an orthocone indicative of an evolutionary branch of the Carboniferous cephalopods described as the order Donovanico- nida Doguzhaeva, Mapes, and Mutvei, 2007a within the subclass Coleoidea Bather, 1888. Here, we describe from that site a bactritoid-like coleoid, Oklaconus okmulgeensis n. gen. n. sp. in Oklaconidae n. fam. A broad lateral lobe of the suture line and a compressed conch with a narrowed dorsal side and a broadly rounded ventral side distinguish this genus from Donovaniconus Doguzhaeva, Mapes, and Mutvei, 2002b. The muscular mantle is preserved as a dense sheet-like structure, with a crisscross pattern and a globular-lamellar ultrastructure. Recent knowledge on the early to late Carboniferous coleoids is discussed. Carboniferous coleoids show a high morphological plasticity with a capacity for being altered to create the diverse combinations of ‘bactritoid’ and ‘coleoid’ structures. This could be the principle evolutionary driver of their radiation in the late Carboniferous.


Introduction


Prior to the current century, the Late Triassic Phragmoteuthis bisinuata von Mojsisovics, 1882 (= Belemnoteuthis of Bronn, 1859;=Acanthoteuthis Suess, 1865) from the Austrian Alps was the oldest coleoid known to have an ink sac (Bronn, 1859; Suess, 1865; von Mojsisovics, 1882; Doguzhaeva et al., 2007c; Doguzhaeva and Summesberger, 2012). Recently, the oldest coleoids with ink sacs have been reported from the lower to upper Carboniferous of North America (Doguzhaeva et al., 2002c, d, 2003, 2004a, 2007a, 2010a; Mapes et al., 2010a, b; Mapes and Doguzhaeva, 2017). These taxa illuminate their high morphological diversity and evolutionary radiation in the late Carboniferous (Doguzhaeva et al., 2010a). Flower and Gordon (1959) described the first Carboniferous


coleoid genera (Hematites, Paleoconus,and Bactritimimus)that were referred to the order Aulacocerida Stolley, 1919 because of the presence of a robust rostrumcovering the phragmocone. Since then, the Middle Pennsylvanian (Moscovian=Desmoinesian) deposits in Illinois (theMazon Creek Lagerstätte) and Oklahoma (Deep Fork River locality) have been the world’s primary Car- boniferous coleoid ‘producers’ of that age (Johnson and Richardson, 1966, 1968; Saunders and Richardson, 1979; Allison, 1987; Kluessendorf and Doyle, 2000; Doguzhaeva et al., 2002b, 2002c, 2007a, 2010b). Recently, the Carboniferous phragmocone-bearing coleoids have been assigned to four orders: Hematitida Doguzhaeva, Mapes, and Mutvei, 2002a; Donovani- conida;Aulacocerida, and Spirulida Pompeckj, 1912, all of which have a small marginal siphuncle, contrary to paracoleoids with a


broad central siphuncle (Doguzhaeva et al., 2017). The present paper is focused on a new late Carboniferous bactritoid-like coleoid fromOklahomawith an ink sac in the body chamber and a muscular mantle on top of the conch. The record of ink sacs in Carboniferous coleoids and a lack of the body chamber in Hematites and its significance for clarifying the origin of a proostracum in belemnoids are also discussed.


Geological setting and environmental conditions


The studied specimen, as well as the earlier described bactritoid- like coleoid Donovaniconus oklahomensis Doguzhaeva, Mapes, and Mutvei, 2002b comes from the Wewoka Formation, Pennsylvanian, Desmoinesian (=late Carboniferous, Moscovian) in Oklahoma, USA. The Oklahoma occurrence is limited to the Deep Fork River locality ~5km to the west of the community of Okmulgee on the western side of the Deep Fork Creek bridge on Oklahoma Highway 56 (see Mapes, 1979, locality P-6, p. 9–10, or locality OKD-10 of Boardman et al., 1994, SE1/4, SE1/4, sec. 10, T. 13N, R. 12E; Okmulgee Lake 7½’ quadrangle). The locality is a fossil-bearing shale bed with a single carbonate concretion layer. This layer yielded the coleoids Donovaniconus and Oklaconus n. gen. The concretions are always longer than thick (maximum and minimum length, ~150mm and 450mm, respectively, and ~70mm thick). They commonly contain diverse ammonoids at all stages of growth, numerous juvenile bactritoids, rare orthoconic and coiled nautiloids, rare cephalopod beaks, the spat of bivalves and gastropods, and fish debris (see Mapes, 1979, locality P-6).


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