identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
7C52D4FC8E9557729464E76E5420FDDA.text	7C52D4FC8E9557729464E76E5420FDDA.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Orthonychia enorme (Lindstroem 1884)	<div><p>Orthonychia enorme (Lindstroem, 1884)</p><p>Figs 3, 4, 5, 6, 7, 8</p><p>1884 Platyceras enorme sp. nov. - Lindström: 69, pl. 2, figs 59-72. cf. 1976 Platyceras (Orthonychia) cf. P. (Orthonychia) enorme Lindström, 1884 - Peel and Yochelson: 17.</p><p>Lectotype.</p><p>Selected here, NRM Mo 38219 from the Eke Formation at Rikvide, Gotland, illustrated by Lindström (1884, pl. 2, figs 60, 61, re-illustrated here in Fig. 3A. The specimen is laterally compressed and incomplete when it comes to height but shows the early ontogeny, the tube-like expansion of the shell and the distinct ornamentation.</p><p>Other type material.</p><p>Lindström (1884) illustrated an additional six specimens from the same locality as the lectotype, and these are here considered paralectotypes (NRM Mo 38218, Mo 38220-Mo 38324); see Figs 3B - 5B. The identity of specimens listed by Lindström (1884) from other localities cannot be established, with the exception of the specimen from Slite which is not conspecific with O. enorme (see below). The other localities mentioned by Lindström (1884) span older strata (Djupvik and Klinteberget = Slite beds of Sheinwoodian/Homerian age; Havdhem and Hammar in Kräklingbo = Hemse beds of Gorstian/Ludfordian age) and younger strata (Burgsvik = the Burgsvik Sandstone just overlying the Eke Formation).</p><p>Additional material.</p><p>Ca. 240 juvenile shells (illustrated material SNSB-BSPG 2023 X 1-15). from the <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=18.192972&amp;materialsCitation.latitude=57.068275" title="Search Plazi for locations around (long 18.192972/lat 57.068275)">Eke Formation</a> at <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=18.192972&amp;materialsCitation.latitude=57.068275" title="Search Plazi for locations around (long 18.192972/lat 57.068275)">Bodudd</a> (S Gotland, Sweden, 57°04'05.8"N, 18° 11'34.7"E, compare Calner et al. 2004, fig. 2) which is <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=18.192972&amp;materialsCitation.latitude=57.068275" title="Search Plazi for locations around (long 18.192972/lat 57.068275)">Ludfordian</a> (Ludlow, upper Silurian) in age .</p><p>Description of type material</p><p>(Figs 3 - 5, Table 1). Largest shell 16.5 mm tall and 7.5 mm in apertural length (in lateral view). On average the shell is twice as tall as long (in lateral view). NRM Mo 38219 (Fig. 3A) deviates by length of aperture being 75% of height, but the shell is laterally compressed. NRM Mo 38222 (Fig. 5B) has an aperture length that is only about 40% of shell height. Rate of expansion high when viewed in a lateral perspective, but less when viewed anteriorly/posteriorly, making aperture sub-oval. Growth lines irregularly crenulated, but overall attitude is straight across posterior section of shell (Figs 3A3, 4A4), gently arched on lateral surfaces and curved into broad median sinus anteriorly. Here the growth lines are sinusoid with two asymmetrical crenulations of which the left has greater amplitude (Figs 3A4, 4A3). Although the intensity and irregularity of the crenulations vary, there are no major deviations from the overall co-marginal alignment. The co-marginal ribs or frills seen in early ontogeny widens into distinct growth increments, spaced less than 1 mm apart and ending in seemingly short lamellae. Fine radial striae may be present within each growth increment. Specimen NRM 38220 appears to have a mostly smooth shell with fine growth lines only, but increments with lamellae are visible on the initial part of the shell (Figs 3B3, B4). Space between increments get narrower in late ontogeny (Fig. 4A, B). Radial ornamentation is absent.</p><p>Description of additional material from sieved bulk samples</p><p>(juvenile and encrusted shells, Figs 6 - 8). Shell with tightly coiled ca. 1.5-2.5 initial whorls including protoconch and early teleoconch; largest shell studied with SEM 4.1 mm long, 1.9 mm wide; encrusted specimens (forming cores of oncoids) probably belonging to the present species up to 20 mm long; protoconch with round, convex whorls and slightly elevated spire, lacking ornament (but re-crystallized); encrusted (oncoid) specimens possibly belong to this species up to 20 mm long; diameter of first whorl 0.17-0.25 mm, diameter of protoconch 0.37-0.68 mm (two measurements); protoconch/teleoconch-transition indistinct due to preservation (re-crystallization) but apparent by sudden onset of co-marginal ribs (may also appear as frills or lamellae) and rapid increase of expansion rate of whorl diameter; later teleoconch detaches and becomes uncoiled, bent to slightly elongated, slowly increasing in diameter, forming a cap-shaped tube; teleoconch ornamented by sharp, narrow co-marginal ribs separated by wide interspaces; strength of ribs and density of ribbing variable; ribs can also form lamellae; ribs appear much longer (lamellae) in specimens studied in thin sections than ribs in specimens from bulk samples suggesting that such lamellar ribs broke off during processing of sample; teleoconch also ornamented by thin spiral lirae, much weaker than co-marginal ribs; shell having a calcitic layer as suggested by thin sections.</p><p>Remarks.</p><p>Lindström (1884, p. 69) mentioned several specimens from various localities on Gotland, but figured only specimens from Rikvide. In the NRM collection only specimens from Rikvide and Burgsvik are registered, but specimens from the latter locality were not available for study. The specimen from Slite in the PMU collections, mentioned by Lindström (1884), is illustrated here in Fig. 5B. It comes from the much older Slite Group sediments and is here treated as Orthonychia sp. The species was also listed from the Slite Beds by Manten (1971, table 11). However, it differs markedly from O. enorme in the initial shell having higher rate of coiling, possibly more coiled whorls before extending into the tubular shell, the shell is proportionally broader at the aperture, the W/H ratio is higher (0.65), it lacks clear growth increments and lamellae, and have a distinct radial ornamentation crossing the fine co-marginal growth lines thus creating a fine reticulate pattern. Furthermore, the shell reverses curvature during growth.</p><p>Lindström (1884, p. 69, pl. 2, fig. 71) described and illustrated a fine radial ornamentation. Some faint striations may be discerned in NRM 38218 (Fig. 4B2) but similar ornamentation is not seen in other macro-specimens. Fine and widely spaced lirae are present in early ontogeny (Gotland Ortho 1, C2). The two-element illustration in Lindström (1884) cannot readily be linked to any of the available specimens.</p><p>Peel and Yochelson (1976, p. 17) listed Platyceras (Orthonychia) cf. P. (Orthonychia) enorme Lindström, 1884 from the Telychian of Norway.</p><p>The present material from the bulk samples closely resembles the type material of Platyceras enorme Lindström, 1884 as described and illustrated above. The type specimens are much larger (more than 16 mm long) than the specimens from the washed residue reported here. However, strongly encrusted specimens studied by Schugmann (2015) and herein (Fig. 6) are also in this larger size range suggesting that the specimens from the residues are juveniles. Platyceras cornutum from the upper Silurian of Gotland as illustrated by Lindström (1884) is similar but lacks ornamentation of axial ribs/frills and spiral lirae; instead it has co-marginal irregular bulges. Moreover, the teleoconch of Platyceras cornutum is generally more curved.</p><p>The Devonian Crossoceras Boucot &amp; Yochelson, 1966 ( Platyceratidae) is ornamented with co-marginal sharp ribs (frills) and a fine spiral lineation similar to the ornament of Platyceras enorme . However, Crossoceras has a stronger curvature of the teleoconch and is thus close to Platyceras in this respect. A close phylogenetic relationship of Crossoceras and Orthonychia enorme seems to be likely. The protoconch of Crossoceras is unknown; judging from the illustration given by Boucot and Yochelson (1966, pl. 3, fig. 11) it could be tightly coiled as in Orthonychia enorme but the preservation is insufficient to be sure.</p><p>Pragoserpulina tomasi Frýda, 1998a, type species of Pragoserpulina Frýda, 1998a, family Pragoserpulinidae Frýda, 1998a, from the Early Devonian of the Czech Republic (Dvorce-Prokop Limestone, Praha Formation, Pragian, Czech Republic) closely resembles O. enorme in teleoconch morphology and in having the same type of tightly coiled protoconch. However, the uncoiled teleoconch of P. tomasi is more bent, its ribbing is denser, the co-marginal ribs are stronger; the ribs are rounded and not as sharp (no frills). Bouchet et al. (2005, 2017) classified Pragoserpulinidae as a Paleozoic taxon that certainly belongs to gastropods, unassigned to superfamily - it is possible that Pragoserpulina is platycerate.</p><p>The tightly coiled protoconchs shown here for Orthonychia enorme and that illustrated by Frýda (1998a) for Pragoserpulina tomasi are clearly not of the vetigastropod type (see e. g., Bandel 1982; Haszprunar et al. 1995; Nützel 2014). They probably were produced by larvae with a short-termed planktotrophic phase. Similar protoconchs were reported for the Paleozoic neritimorph Naticopsis ( Nützel and Mapes 2001; Nützel et al. 2007b) and Platyceras ( Frýda et al. 2009). The same type of protoconch was found in Devonian and early Carboniferous gastropods with a cap-shaped teleoconch placed in the family Pragoscutulidae Frýda, 1998a (Cook et al. 2008). They were classified as Caenogastropoda but a neritimorph relation seems also possible. Pragoscutulidae are much stouter i.e., they have a much wider apical angle.</p></div>	https://treatment.plazi.org/id/7C52D4FC8E9557729464E76E5420FDDA	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Pensoft via Plazi	Nuetzel, Alexander;Ebbestad, Jan Ove;Seuss, Barbara;Munnecke, Axel;Mapes, Royal H.;Cook, Alex G.	Nuetzel, Alexander, Ebbestad, Jan Ove, Seuss, Barbara, Munnecke, Axel, Mapes, Royal H., Cook, Alex G. (2023): On Paleozoic platycerate gastropods. Zitteliana 97: 29-51, DOI: http://dx.doi.org/10.3897/zitteliana.97.115688, URL: http://dx.doi.org/10.3897/zitteliana.97.115688
6AF9492D914E5254AF8AD70398F1D7B2.text	6AF9492D914E5254AF8AD70398F1D7B2.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Orthonychiidae Hall 1843	<div><p>Family Orthonychiidae Bandel &amp; Fryda, 1999</p><p>Remarks.</p><p>Bandel and Frýda (1999) erected this family for limpet-shaped Paleozoic gastropods formerly included in Platyceratidae . Based on the openly coiled fishhook-like protoconch of the Pennsylvanian limpet-shaped species Orthonychia parva (Swallow, 1858 in Shumard and Swallow), they placed Orthonychiidae in their new order Cyrtoneritimorpha . However, the protoconch of the Devonian type species of Orthonychia is yet unknown (see Knight 1941). The Ordovician family Pollicinidae resembles some members of Orthonychiidae but these shells are bilaterally symmetrical and their early ontogeny is largely unknown (see Peel 2020a, b).</p></div>	https://treatment.plazi.org/id/6AF9492D914E5254AF8AD70398F1D7B2	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Pensoft via Plazi	Nuetzel, Alexander;Ebbestad, Jan Ove;Seuss, Barbara;Munnecke, Axel;Mapes, Royal H.;Cook, Alex G.	Nuetzel, Alexander, Ebbestad, Jan Ove, Seuss, Barbara, Munnecke, Axel, Mapes, Royal H., Cook, Alex G. (2023): On Paleozoic platycerate gastropods. Zitteliana 97: 29-51, DOI: http://dx.doi.org/10.3897/zitteliana.97.115688, URL: http://dx.doi.org/10.3897/zitteliana.97.115688
B218C5B73C58578AA3889ED788410843.text	B218C5B73C58578AA3889ED788410843.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Orthonychia Hall 1843	<div><p>Genus Orthonychia Hall, 1843</p><p>Type species.</p><p>Platyceras subrectum Hall, 1859; by subsequent monotypy by Hall (1859).</p><p>Remarks.</p><p>Orthonychia is a cap-shaped or elongate tube-like mollusk which has traditionally been placed in the in the Paleozoic gastropod family Platyceratidae and was also considered a subgenus of Platyceras (Knight et al. 1960). The Devonian type species of Orthonychia, O. subrecta (Hall, 1859), is known from steinkerns only (Knight 1941) and therefore, the status of shell ornamentation and protoconch morphology cannot be assessed. The general habitus (elongated slightly curved shell with only the early teleoconch being coiled) is close to that of Orthonychia enorme ( Lindström, 1884) and Orthonychia yutaroi Ebbestad, sp. nov. as described below, especially regarding the tube-shaped, stretched late teleoconch. Based on an openly coiled fish-hook-like protoconch, present in the Pennsylvanian species O. parva, Bandel and Frýda (1999) erected the family Orthonychiidae and placed it in a new order Cyrtoneritimorpha, forming the fossil sister group of modern Neritimorpha ( Cycloneritimorpha).</p><p>The tall shell morphology of some Orthonychia species including O. yutaroi and O. enorme as reported herein superficially resembles that of the Ordovician archaeogastropod Pollicina, described by Peel (2020a, b). This genus can reach a height of at least 3 cm, has a thick shell, with even co-marginal ribs, and an apex truncated by septa. The shell is bilaterally symmetrical, in contrast to that of Orthonychia .</p></div>	https://treatment.plazi.org/id/B218C5B73C58578AA3889ED788410843	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Pensoft via Plazi	Nuetzel, Alexander;Ebbestad, Jan Ove;Seuss, Barbara;Munnecke, Axel;Mapes, Royal H.;Cook, Alex G.	Nuetzel, Alexander, Ebbestad, Jan Ove, Seuss, Barbara, Munnecke, Axel, Mapes, Royal H., Cook, Alex G. (2023): On Paleozoic platycerate gastropods. Zitteliana 97: 29-51, DOI: http://dx.doi.org/10.3897/zitteliana.97.115688, URL: http://dx.doi.org/10.3897/zitteliana.97.115688
63E480A487FC513EB6B0F7E8ED9C5D97.text	63E480A487FC513EB6B0F7E8ED9C5D97.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Orthonychia parva (Swallow 1858)	<div><p>Orthonychia parva (Swallow, 1858 in Shumard and Swallow)</p><p>Figs 9, 10, 11, 12</p><p>*1858 Capulus parvus sp. nov. - Swallow (in Shumard and Swallow): 205.</p><p>1967 Platyceras (Orthonychia) parvum (Swallow, 1858) - Yochelson and Saunders: 173 [additional synonymy and chresonymy therein].</p><p>1999 Orthonychia parva (Swallow, 1858) - Bandel and Frýda: text-fig. 1, pl. 2, figs 5-8, pl. 3 figs 1-2.</p><p>2005 Orthonychia parva - Frýda: 382, fig. 3D.</p><p>2008a Orthonychia parva - Frýda et al.: 254, fig. 10.8E, G.</p><p>2009 Orthonychia parva (Shumard &amp; Swallow, 1858) - Frýda et al.: 112, 116, fig. 5C-D.</p><p>2012 Orthonychia parva - Frýda et al.: 417, fig. 14E, M.</p><p>2014 Pseudorthonychia - Nützel: 491, fig. 14E, H.</p><p>Material.</p><p>6 specimens (SNSB-BSPG 2020 XCI 117-122) from the <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=-98.136&amp;materialsCitation.latitude=33.23" title="Search Plazi for locations around (long -98.136/lat 33.23)">Finis Shale Member</a> of the <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=-98.136&amp;materialsCitation.latitude=33.23" title="Search Plazi for locations around (long -98.136/lat 33.23)">Graham Formation</a> (late <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=-98.136&amp;materialsCitation.latitude=33.23" title="Search Plazi for locations around (long -98.136/lat 33.23)">Pennsylvanian</a>, <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=-98.136&amp;materialsCitation.latitude=33.23" title="Search Plazi for locations around (long -98.136/lat 33.23)">Virgillian</a>, <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=-98.136&amp;materialsCitation.latitude=33.23" title="Search Plazi for locations around (long -98.136/lat 33.23)">North Central</a> Texas, USA) at the locality TXV-200: <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=-98.136&amp;materialsCitation.latitude=33.23" title="Search Plazi for locations around (long -98.136/lat 33.23)">Lost Creek Lake</a> emergency spillway at dam, approximately 4 km northeast of <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=-98.136&amp;materialsCitation.latitude=33.23" title="Search Plazi for locations around (long -98.136/lat 33.23)">Jacksboro</a>, Jack County, Texas on Texas <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=-98.136&amp;materialsCitation.latitude=33.23" title="Search Plazi for locations around (long -98.136/lat 33.23)">Highway</a> 59. AMNH Locality 5562, 33°14'11.17"N, 98°07'11.33"W, 33.230, -98.136 .</p><p>Description.</p><p>Shell limpet-shaped; protoconch (description largely based on SNSB-BSPG 2020 XCI 117, Figs 9A, 12) with an initial bulb (Fig. 12 I) slightly elongated, 100-120 µm long, 70-75 µm wide, terminating in a slight constriction; width of initial bulb at 100 µm shell length 70-80 µm; shell after initial bulb forming a straight tube slowly increasing in width (Fig. 12 II); dextral coiling starts at 270-360 µm shell length and coiling comprises 100-180° (Fig. 12 III) until strong co-marginal ribs develop on the shell; the smooth initial shell has the form of a hook that encloses a central gap i. e., it is openly coiled; terminal width of whorl of initial smooth shell 0.5-0.6 mm; smooth initial whorl followed by rapidly expanding shell portion with strong collabral ribs (Fig. 12 IV); ribs separated by wider interspaces, prosocyrt in apical view and prosocline in lateral view; initial smooth shell part resting on axially ribbed shell; shell part with strong axial ribs has width of 0.8-1 mm at termination; shell distinctly and abruptly widening after initial shell with axial ribs resulting in a cap-shaped morphology (Fig. 12 V), transition at an angle; following shell cap-shaped with variable co-marginal ornament; one specimens shows fine longitudinal lirae on the teleoconch (Fig. 10B6).</p><p>Discussion.</p><p>Orthonychia parva is widely distributed throughout the Carboniferous of the US (Yochelson and Saunders 1967). It has also been reported from the Pennsylvanian of North Central Texas (Mineral Wells Fm.) (Plummer and Moore 1921) although not from the Finis Shale. To our knowledge, Knight (1934, figs 1d-g) reported the only specimens (four) with preserved protoconchs. Two of these specimens were also illustrated in detail (SEM) by Bandel and Frýda (1999, pl. 2 figs 5-8): (reproduced by Frýda 2005, fig. 3D; Frýda et al. 2008a, fig. 10.8 E, G; Frýda 2012, fig. 14E,M; Nützel 2014, fig. 14E, H, erroneously as Pseudorthonychia). The same type of protoconch with stretched initial part and open coiling has been reported for the Devonian Praenatica cheloti by Frýda et al. (2009).</p><p>The present shell displays considerable ontogenetic change. There can be little doubt that the initial bulb represents the embryonic shell as was also concluded by Bandel and Frýda (1999), Frýda et al. (2008b), and Frýda (2012). Its small size of 100-120 µm × 70 µm suggests indirect, planktotrophic larval development. The question is at which stage the larval shell terminates and the teleoconch starts. Knight (1934) for the first time reported and described this type of protoconch and noticed its morphology which is unusual for gastropods ('curious vermiform nuclei’). He described the ‘nucleus’ as a narrow vermiform hook of one smooth revolution. The abrupt expansion of the shell which then bears co-marginal ribs was called by him ‘neanic’ i. e., as representing the early juvenile teleoconch. By contrast, based on the restudy of Knight’s (1934) material from the Labette Shale, Bandel and Frýda (1999) and Frýda (2012) assumed that the axially ribbed part following the smooth hook-like shells belongs to the larval shell. Here, we follow Knight’s (1934) interpretation because the smooth shell terminates abruptly and the size of the following axially ribbed portion of the shell (here Fig. 12 IV) has a width of ca. 2 mm at its termination which is too large for a larval shell. Hence the larval shell of O. parva comprises portions I-III as given in Fig. 12.</p><p>The change from a straight narrow tube to a coiled tube (Fig. 12 II to III) is readily explained: it would be highly disadvantageous for the pediveliger to settle with an entirely straight narrow tube (stretched, uncoiled shell tube would probably be vulnerable and hinder locomotion) and therefore coiling in the last period of larval life does make sense as a preparation for benthic life. The early axially ribbed teleoconch was probably formed by the crawling juvenile and the sudden widening of the shell could indicate the start of the sedentary life on crinoids.</p></div>	https://treatment.plazi.org/id/63E480A487FC513EB6B0F7E8ED9C5D97	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Pensoft via Plazi	Nuetzel, Alexander;Ebbestad, Jan Ove;Seuss, Barbara;Munnecke, Axel;Mapes, Royal H.;Cook, Alex G.	Nuetzel, Alexander, Ebbestad, Jan Ove, Seuss, Barbara, Munnecke, Axel, Mapes, Royal H., Cook, Alex G. (2023): On Paleozoic platycerate gastropods. Zitteliana 97: 29-51, DOI: http://dx.doi.org/10.3897/zitteliana.97.115688, URL: http://dx.doi.org/10.3897/zitteliana.97.115688
F47976FB9D855B8CA78608AB0AAF11E6.text	F47976FB9D855B8CA78608AB0AAF11E6.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Orthonychia sp.	<div><p>Orthonychia sp.</p><p>Fig. 13A, B</p><p>Material.</p><p>Two specimens from the Upper Mississippian (Chesterian) Imo Formation, Arkansas (SNSB-BSPG 2023 I 89, SNSB-BSPG 2023 I 90). The material was sampled by R. H. Mapes (ARC-02, samples Imo-6 and Imo-8.) at the Location #1 as given by Jeffery et al. (1994), figs 1 and 2). This location, the Peyton Creek Roadcut, was also described in detail by Manger (1977) who measured a section in the outcrop (Manger 1977, fig. 1). The sample Imo-6 sample came from position 20 in this section, approximately 110 feet above the base of his measured section and the Imo-8 sample came from position 24, which is about 135 feet above the base of his measured section. NE1/4 sec. 11 and NW1/4 sec. 12, T. 13 N., R. 15 W. Van Buren County, Arkansas</p><p>Description.</p><p>Juvenile shell 0.66 mm wide, 0.52 mm high; shell starts with a slightly elongated initial bulb with a length of 87 µm and a width of 63 µm; width of shell at shell length 100 µm is 66-68 µm; initial bulb is bent slightly adapically in relation to the following straight shell-tube; following shell is an entirely straight, smooth tube that increases slowly in diameter. At a total shell length of 320 µm the tube starts a sharp coiling in a dextral direction and at the same time, it is strongly expanding in diameter; shell is smooth except of a faint micro-striation visible on the coiled part of the first whorl.</p><p>Remarks.</p><p>We suppose that approximately the first openly coiled whorl represents the larval shell and that the faint micro-striation is the larval shell ornament. The protoconch of this species resembles the above described Orthonychia parva by having an initial bulb, representing most likely the embryonic shell (protoconch 1) and a following straight tube. However, the early shell of Orthonychia sp. lacks any strong co-marginal ribs or frills. Among the gastropod species described from the Imo Formation by Jeffery et al. (1994), Platyceras ( Orthonychia ?) sp. is the most likely candidate to be conspecific with the two juvenile specimens studied herein. They reported a single specimen from their rich collections and thus the species is very rare in this fauna.</p></div>	https://treatment.plazi.org/id/F47976FB9D855B8CA78608AB0AAF11E6	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Pensoft via Plazi	Nuetzel, Alexander;Ebbestad, Jan Ove;Seuss, Barbara;Munnecke, Axel;Mapes, Royal H.;Cook, Alex G.	Nuetzel, Alexander, Ebbestad, Jan Ove, Seuss, Barbara, Munnecke, Axel, Mapes, Royal H., Cook, Alex G. (2023): On Paleozoic platycerate gastropods. Zitteliana 97: 29-51, DOI: http://dx.doi.org/10.3897/zitteliana.97.115688, URL: http://dx.doi.org/10.3897/zitteliana.97.115688
F4E29B18A8415F0083385677AF802DA5.text	F4E29B18A8415F0083385677AF802DA5.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Orthonychia yutaroi Ebbestad 2023	<div><p>Orthonychia yutaroi Ebbestad sp. nov.</p><p>Fig. 2</p><p>Material.</p><p>Only the holotype (PMU 37146) is known, from the Late Ordovician (Katian) Boda Limestone at Jutjärn quarry, Siljan district, Dalarna .</p><p>Derivation of name.</p><p>After Dr Yutaro Suzuki, Shizuoka University, Japan, who found the specimen and who has made extensive studies of fossils and the mound ecology of the Boda Limestone.</p><p>Diagnosis.</p><p>Shell tall, teleoconch forming a weakly cyrtoconic tube, open coiled with apex coiled through half a whorl; supra-apical surface formed by raised and convex median section; teleoconch ornamentation consist of densely spaced, slightly undulating, strong co-marginal ribs on initial parts, widening later in ontogeny to distinct growth increments that end in a flared lamellae; growth lines corrugated, laterally forming two or three spaced flutes, across the median part only weakly undulating; last part of protoconch without visible ornament and abrupt transition to teleoconch; early protoconch whorls poorly preserved as imprint, possibly tightly coiled consisting of ca. two whorls.</p><p>Description.</p><p>Shell tall, weakly cyrtoconic, open coiled with apex coiled through at least half a whorl before shell coiling ends and a straight tube forms, widening gradually with length at base about 45% of total height (= 20 mm). Shell nearly planispiral but with weak translation down the axis if viewed with aperture in normal right-handed position. Apex overhang sub-apical margin. Supra-apical surface of shell forms a raised and convex median section, with concave transition to lateral surfaces. Ornamentation on initial conch consist of densely spaced, slightly undulating, strong co-marginal ribs. A couple of millimeters from the apex, the space between the ribs widens gradually and distinct growth increments (here taken as the growth accumulated in the space between subsequent lamellae) become apparent. Increments are spaced no more than 1 mm apart, consist of fine co-marginal growth lines and end with a lamella that extends prominently and nearly horizontal from the shell (arrows in Fig. 2A4, A5). Near the aperture the space between the increments again becomes narrower. The growth lines are corrugated, laterally forming two or three spaced flutes that have a pointed bell-shaped, whereas the growth lines across the median part only are weakly undulating. Ornamentation on inner margin obscured by matrix. Medially the growth-lines form a broad low-relief U-shape.</p><p>Last part of protoconch without visible ornament and abrupt transition to teleoconch; width of last protoconch whorl at termination about 200 µm; early protoconch whorls poorly preserved as imprint, possibly tightly coiled consisting of ca. two whorls.</p><p>Remarks.</p><p>The conch of Orthonychia yutaroi resembles an orthonychian shell morphology in the tall elongated tube-like shell and has a similar crenulated teleoconch ornamentation as the Silurian O. enorme (see below). Compared with O. enorme it differs markedly in attaining an open coiled shell earlier, as the initial shell of O. enorme coils more tightly. However, the teleochonch in O. yutaroi expands more slowly in late ontogeny than that of O. enorme and the shell of the Dalarna species is proportionally taller and straighter (less pronounced supra-apical curvature). The periodic flaring lamellae in Orthonychia yutaroi are much more extensive and more pronounced, and ribbing is much denser, especially in the early teleoconch, than in O. enorme . Furthermore, O. yutaroi has stronger crenulations forming flutes laterally, whereas the longitudinal flutes are weak or absent in O. enorme . But both species share the development of periodic growth increments that end with a crenulated lamella.</p><p>The protoconch of Orthonychia yutaroi is incompletely preserved but it is clear that it lacks visible ornament and has an abrupt transition to the teleoconch. It seems to be possible that the protoconch is tightly coiled and consists of ca. 2.5 whorls, similar to what we have found in O. enorme (see below).</p></div>	https://treatment.plazi.org/id/F4E29B18A8415F0083385677AF802DA5	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Pensoft via Plazi	Nuetzel, Alexander;Ebbestad, Jan Ove;Seuss, Barbara;Munnecke, Axel;Mapes, Royal H.;Cook, Alex G.	Nuetzel, Alexander, Ebbestad, Jan Ove, Seuss, Barbara, Munnecke, Axel, Mapes, Royal H., Cook, Alex G. (2023): On Paleozoic platycerate gastropods. Zitteliana 97: 29-51, DOI: http://dx.doi.org/10.3897/zitteliana.97.115688, URL: http://dx.doi.org/10.3897/zitteliana.97.115688
