Lochriea monocarinata, Zhuravlev, 2024

Zhuravlev, Andrey V., 2024, A new species, Lochriea monocarinata n. sp., and its position in the morphospace of the genus Lochriea Scott, 1942 (Conodonta, Mississippian), Geodiversitas 46 (18), pp. 955-965 : 961

Lochriea monocarinata n. sp.

( Fig. 5N, P, R, S, U-W, Z )

urn:lsid:zoobank.org:act:76E819C9-6E67-454A-BA37-C8CEA4BAF80E

Gnathodus nodosus – Metcalfe 1981: 47, pl. 7, fig. 3.

Paragnathodus monocostatus – Kulagina et al. 1992: pl. XXIX, fig. 7.

Lochriea sp. – Barham et al. 2015: 15, figs 11.1, 11.12, 11.4, 11.5, 11.7.

Lochriea sp. – Wang et al. 2018: 438, figs 3.53, 3.54.

Lochriea monocostata – Nikolaeva et al. 2020: fig. 12J.

ETYMOLOGY. — According to the ornamentation of basal cup represented by a single ridge.

TYPE MATERIAL. — Russia • North Cis-Urals, Tchenyshev Ridge, Izyayu section; 65°33’9.53”N, 58°38’50.32”E; Mississippian, early Serpukhovian, L. ziegleri Zone; holotype: specimen 445/12, sample Iz4-52/98 ( Fig. 5Z ), housed in Chernov Museum of Institute of Geology FRC Komi SC UrB RAS, Syktyvkar .

TYPE LOCALITY. — Izyayu section, Tchenyshev Ridge, North Cis-Urals, Russia (65°33’9.53”N, 58°38’50.32”E).

TYPE AGE. — Mississippian, early Serpukhovian, L. ziegleri Zone.

DIAGNOSIS. — Species of Lochriea with P1 element bearing the nodose ridge on the inner (caudal) part of the asymmetrical basal cup.

MATERIAL EXAMINED. — Nine specimens from the Serpukhovian of North Urals and North Cis-Urals.

DISTRIBUTION. — The new species is known from the lower Serpukhovian ( L. ziegleri Zone ) of the North Cis-Urals, SubPolar Urals, South Urals (Eastern Laurussia), Rhenish Mountains ( Wang et al. 2018), northwest Ireland ( Barham et al. 2015) and Craven Lowlands of northern England ( Metcalfe 1981) (Southern Laurussia).

DESCRIPTION

The carminiscaphate P1 element has a basal cap located near the posterior (dorsal) end. Carina is high with denticles of almost uniform height. Upper part of denticles in posterior part of carina is broad and bears pustulation. Cup is asymmetrical and bears the nodose crenulated ridge on the inner (caudal) side.

Sinistral and dextral P1 elements compose an almost symmetrical pair (transition from Class II symmetry to Class III symmetry). The dextral elements are characterised by less cup asymmetry and a ventrally displaced nodose ridge ( Fig. 6 E-G). The sinistral elements show a more developed ridge ornamentation compared to the dextral elements at the same stage of ontogeny ( Fig. 6 A-D). Sinistral P1 elements have isometric nodes on ridge, but dextral P1 elements have elongated nodes on ridge. This difference in node shape probably provides better occlusion of the sinistral and dextral elements. The asymmetry of the sinistral and dextral P1 elements ensures that they are occluded in the apparatus in a “dextral in front of the sinistral” pattern ( Fig. 6H ). The apparatus composition of the new species has not yet been reconstructed. Lochriea monocarinata n. sp. probably shares S, M, and P2 elements with other advanced representatives of the genus Lochriea (e.g. Fig. 5 AA).

REMARKS

The new species differs from Lochriea monocostata by distinct crenulate nodose ornamentation on the inner ridge. Transitional forms from L. monocostata to L. monocarinata n. sp. possess weak nodose ornamentation of the costa consisting of one or two small and smooth nodes ( Fig. 5Y ) (see also Nemirovskaya et al. 1994: pl. 2, fig. 3; Nemyrovska et al. 2011: pl. 2, fig. 2; Nikolaeva et al. 2020: fig. 12A). The morphological transitions from L. mononodosa to L. monocarinata n. sp. ( Fig. 5Q ) and from L. monocarinata n. sp. to L. ziegleri ( Fig. 5J ) also occur. Lochriea monocarinata n. sp. can be distinguished from L. mononodosa and L. monocostata by the presence of at least three crenulate nodes forming the ridge. The ornamentation of the P1 elements of L. monocarinata n. sp. in the early stages of ontogeny is almost identical to that of L. monocostata or L. mononodosa . If the nodes are crenulated, specimens with a ridge decorated with two nodes in the early stages of ontogeny can be identified as L. monocarinata n. sp. (e.g. Figs 5Q ; 6A, E ).

Figures

FIG. 5. — Some advanced Lochriea from the Serpukhovian (Lochriea ziegleri Zone) of North of Urals and Cis-Urals region: A, Lochriea ziegleri Nemirovskaya, Perret-Mirouse, Meischner, 1994, specimen 145/24, sample Iz4-51/98, Izyayu section; B, Lochriea ziegleri Nemirovskaya, Perret & Meischner, 1994, specimen 145/19, sample K99-21/22, Kamenka section; C, Lochriea senckenbergica Nemirovskaya, Perret & Meischner, 1994, specimen 145/22, sample 125-19/22, Kamenka section; D, Lochriea ziegleri Nemirovskaya, Perret & Meischner, 1994, specimen 145/20, sample K99-21/22, Kamenka section; E, Lochriea senckenbergica Nemirovskaya, Perret & Meischner, 1994-Lochriea cruciformis (Clarke, 1960) transition, specimen 145/23, sample Iz4-52/98, Izyayu section; F, Lochriea senckenbergica Nemirovskaya, Perret & Meischner, 1994 – Lochriea cruciformis (Clarke, 1960) transition, specimen 145/27, sample Iz4-53/98, Izyayu section; G, Lochriea mononodosa (Rhodes, Austin & Druce, 1969), specimen 145/15, sample N2-1-11/99, Bolshaya Nadota section; H, Lochriea sp., specimen 145/12 sample N2-1-7/99, Bolshaya Nadota section;I, Lochriea ziegleri Nemirovskaya,Perret & Meischner,1994,specimen 145/18, sample K99-21/22,Kamenka section; J, Lochriea monocarinata n. sp.-Lochriea ziegleri Nemirovskaya, Perret & Meischner, 1994 transition, specimen 145/14, sample N2-1-10/99, Bolshaya Nadota section; K, Lochriea monocostata (Pazukhin & Nemirovskaya in Kulagina et al., 1992), specimen 145/4, sample Iz4-53/98, Izyayu section; L, Lochriea mononodosa (Rhodes,Austin & Druce,1969), specimen 145/8, sample Iz4-52/98,Izyayu section;M, Lochriea ziegleri Nemirovskaya, Perret & Meischner,1994,specimen 145/21, sample K99-21/22, Kamenka section; N, Lochriea monocarinata n. sp., specimen 145/16, sample N2-1-11/99, Bolshaya Nadota section; O, Lochriea commutata (Branson & Mehl, 1941)-Lochriea mononodosa (Rhodes, Austin & Druce, 1969) transition, specimen 145/11, sample N2-1-5/99, Bolshaya Nadota section; P, Lochriea monocarinata n. sp., specimen 145/17, sample N2-1-11/99, Bolshaya Nadota section; Q, Lochriea mononodosa (Rhodes, Austin & Druce, 1969)-Lochriea monocarinata n. sp. transition,specimen 145/3,sample Iz4-53/98, Izyayu section;R, Lochriea monocarinata n. sp., specimen 145/7, sample Iz4- 52/98, Izyayu section; S, Lochriea monocarinata n. sp., specimen 145/6, sample Iz4-52/98, Izyayu section; T, Lochriea mononodosa (Rhodes, Austin & Druce, 1969)-Lochriea monocarinata n. sp. transition, specimen145/9, sample Iz4-60/98, Izyayu section; U, Lochriea monocarinata n. sp., specimen 145/10, sample N2-1-5/99, Bolshaya Nadota section; V, Lochriea monocarinata n. sp., specimen 145/2, sample Iz4-53/98, Izyayu section; W, Lochriea monocarinata n. sp., specimen 145/1, sample K99-21/22, Kamenka section; X, Lochriea mononodosa (Rhodes, Austin & Druce, 1969), specimen 145/25, sample Iz4-45/98, Izyayu section; Y, Lochriea monocostata (Pazukhin & Nemirovskaya in Kulagina et al., 1992)-Lochriea monocarinata n. sp. transition, specimen 145/13, sample N2-1- 8/99, Bolshaya Nadota section; Z, Lochriea monocarinata n. sp., holotype, specimen 445/12, sample Iz4-52/98, Izyayu section; AA, Lochriea sp., P2 element, specimen 145/26, sample Iz4-51/98, Izyayu section. Scale bar: 0.1 mm.

FIG. 6. — Morphological schemes of sinistral (A-D) and dextral (E-G) P1 elements of Lochriea monocarinata n. sp. and scheme of probable occlusion of sinistral (red) and dextral (green) elements (H). The line drawings are based on the SEM microphotographs (see Fig. 5). D, holotype, specimen 445/12. Abbreviations: d, dextral; s, sinistral.