Tiaracrinus jeanlemenni, Klug & Baets & Naglik & Waters, 2014

Klug, Christian, Baets, Kenneth De, Naglik, Carole June & Waters, Johnny, 2014, A new species of Tiaracrinus from the latest Emsian of Morocco and its phylogeny, Acta Palaeontologica Polonica 59 (1), pp. 135-145 : 141-142

Tiaracrinus jeanlemenni sp. nov.

Fig. 2 .

1990 Tiaracrinus rarus ( Barrande, 1887) ; Le Menn 1990: 162, pl. 1.

Etymology: After Jean Le Menn, honouring his work on Palaeozoic echinoderms and his thorough description of the genus in Africa.

Type material: Holotype: PIMUZ 29739 , a well-preserved calyx but lacking the oral surface . Paratypes: PIMUZ 29741 , GFCL 2152–2153, LPB 16795.

Type locality: “Red cliff” at Hamar Laghdad (eastern Anti-Atlas, Morocco) .

Type horizon: Probably late Polygnathus patulus Conodont Biozone , late Anarcestes lateseptatus Ammonoid Biozone , latest Emsian, Early Devonian ( Bultynck and Walliser 2000; Klug 2002).

Diagnosis.— Tiaracrinus with a more or less spherical calyx, with four very broad rhomboid radial rib-fields, which are strongly vaulted and which carry a large number of slender ribs (>20), a small and narrow radial ring, narrow and with slightly concave radial channels.

Description.—For the description of the Algerian specimens see Le Menn (1990). The two new Moroccan specimens are described below. Specimen PIMUZ 29739, holotype ( Fig. 2A ). The specimen preserves only the broad subglobular calyx and measures 9 mm in height and maximally 12.9 mm in width. At the oral surface, the width of the calyx is reduced to 8.7 mm, but the oral surface is not preserved. The radial rib-field is up to 9.3 mm wide and it carries up to 22 ribs with pores at the end. In some parts, the ribs carry tubercles, but this might be due to weathering. The four radial channels form a perfect cross when seen from the aboral side. Specimen PIMUZ 29741, paratype ( Fig. 2B ). This calyx also lacks the oral surface, arms, and the stem. With a calyx height of 8.5 mm, this specimen is only 9.6 mm wide and therefore more slender than the holotype and the Algerian specimens. Although this specimen is slightly deformed, this difference in shape is probably original rather than a taphonomic artefact. At the oral surface, it measures only 5 mm while the other three specimens measure 8 mm or more. The ribs in the diamond-shaped rib-field appear finer but are more numerous (24) than in the other specimens. The radial channels also form a perfect cross when seen from the oral side and the rib-fields form a right angle where the channels meet.

Discussion.— Le Menn (1990) listed the five species Tiaracrinus moravicus , T. rarus , T. quadrifrons , T. soyei , and T. tedraedra . His assignment of the three Algerian calices to Barrande’s (1887) species T. rarus was based on the globular calyx with the large number of ribs and the rhomboid rib-fields, which are similar to the European species T. rarus . Both the bivariate plots ( Fig. 3) and the PCA-plots of principal component 1 and 2 as well as of principal component 2 and 3 ( Fig. 4 ) revealed, however, that all specimens of the new species plot in a field separate from those of T. rarus and the other species. By contrast, both in the cluster analysis Fig. 5 ) and in the plot of principal component 1 and 3 ( Fig. 4 ), the specimen from Jebel Oufatene (PIMUZ 29741) falls in the field of T. rarus .

The results of this cluster analysis ( Fig. 5 ) of 15 specimens revealed three pairs of species, which plot in the same respective clusters (see also the phylogeny chapter). In this analysis ( Fig. 5 ), T. rarus is the sister species of T. jeanlemenni . This is also supported by the PCA (especially the principal component 3, i.e., the width size-class and the row ratio) and the bivariate plots ( Figs. 3, 4 ). The separation of T. jeanlemenni from T. rarus is based mainly on the higher number of pore rows ( Fig. 3C) and the lower height to width ratio in the new species.

Morphologically, the Algerian specimens ( Le Menn 1990: pl. 1: 1–12) strongly resemble PIMUZ 29739 from Hamar Laghdad, while the slightly smaller specimen PIMUZ 29741 from Jebel Oufatene looks slightly different ( Fig. 2 ). The question arises, whether this last mentioned specimen belongs to a separate species because it has more ribs with epispires than the other four specimens and the calyx is more slender, which might, however, be due to the slight traces of compaction or due to intraspecific variability (which cannot be quantified due to the low number of available specimens). It resembles T. rarus in the narrower oral surface but it differs from this Bohemian species in the adorally converging radial channels. Nevertheless, most of its measurements and values ( Fig. 3; pore rows in relation to size, height in relation to width) plot very close to the other specimens assigned to the new species ( Fig. 3, 4 ), and therefore we conclude that it belongs to the new species and simply represents a morphological variant.

Stratigraphic and geographic range.—Late Emsian of the eastern Anti-Atlas ( Morocco) and Monts d’Ougarta ( Algeria).

Figures

Fig. 2. Zophocrinid crinoid Tiaracrinus jeanlemenni sp. nov., probably late Polygnathus patulus Conodont Biozone, late Anarcestes lateseptatus Ammonoid Biozone, latest Emsian, Early Devonian, eastern Anti-Atlas Morocco. A. PIMUZ 29739, holotype, “Red cliff” at Hamar Laghdad, Tafilalt. Lateral views (A1, A2), showing the radial channel and the rib-fields; note the ornamentation in the channel near the oral surface in A2. Aboral view (A3), note the small cross section of the trimeral basals and the low rim around it. Oral view (A4), note the ornamentation in the channel near the oral surface. Detail of A3 (A5), note the epispires and the uniform thickness of the ribs. On the top right, the subtle striation is faintly visible between the ribs. Oblique view of the aboral side (A6), showing the epispires. Due to weathering, the ribs obtained a tuberculate ornament (A7). B. PIMUZ 29741, paratype, Jebel Oufatene, Maïder. Aboral view (B1), the rib-fields are less vaulted and the cross section of the calyx less quadrate than in the holotype; the fossil on the top left is a spiriferid. Lateral views (B2, B3), showing the narrow ribs and the smooth surface of the radial channels; in the lateral aspect it looks like the radial channel is tapering towards the oral side of the cup.

Fig. 4. PCA of some published (Le Menn 1190; Hauser 2008) and the two newly described specimens of Tiaracrinus (see Table 1). See Methods for definition of the parameters. A. Plot of principal components 1 and 2; note, how the new species separates well from the previously known ones. B. Plot of principal components 1 and 3. C. Plot of principal components 2 and 3; again, the new species is morphologically separated from the others. Open circles mark the values of the new species T. jeanlemenni sp. nov., solid squares mark all other species.

Fig. 5. Cluster analysis (Euclidean, paired group) of some published specimens and the two newly described specimens (see Table 1). The cluster on the right including Tiaracrinus quadrifrons and Tiaracrinus tetraedra is supported by the bootstrap (at 500 replicates; 59%with past); the Tiaracrinus oehlerti and Tiaracrinus moravicus-group (59 and 64%) and the Tiaracrinus jeanlemenni and Tiaracrinus rarus-group (62 and 72%) are also reasonably well supported. See also the methods chapter for definition of the parameters.