Paraostenia voultensis Secretan 1985
Creators: name: Laville, Thomas
name: Forel, Marie-Béatrice
name: Charbonnier, Sylvain
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Dollocarididae
Paraostenia
Paraostenia voultensis

description: Paraostenia voultensis Secrétan, 1985
Figs 5D, 16–20
Paraostenia voultensis Secrétan, 1985: 388–389, fig. 5c–h, l.
cf. Ostenia sp. – Secrétan & Riou 1983: 26–27, figs 1, 6–7.
Paraostenia voultensis – Rolfe 1985: fig. 4; 1992: fig. 1a. — Schram et al. 1999: 772, tab. 1. — Charbonnier 2009: 206, figs 233, 251, 339–340, tab. 14. — Charbonnier et al. 2010: 115, 121, fig. 5e, tabs 1–2; 2014: 375, tab. 1. — Schram 2014: 353, fig. 3d. — Ji et al. 2017: 174. — Ehiro et al. 2019: 330. — Rak et al. 2018: 268. — Braig et al. 2019: fig. 5.6, 5.31. — Van Roy et al. 2021: 1739. — Laville et al. 2021a: 310–311; 2021b: 92–94; 2021c: 305. — Schram & Koenemann 2022: fig. 41.4, tab. 41.2.
Original diagnosis (Secrétan 1985)
As for genus.
Emended diagnosis
Paraostenia with a serrate dorsal margin and a dorso-lateral row of pores.
Material examined
Holotype FRANCE • La Boissine, La Voulte-sur-Rhône, Ardèche; Callovian, Middle Jurassic; morphotype 2; MNHN.F. R50977.
Paratype FRANCE • 1 spec.; same collection data as for holotype; MNHN.F. R50979.
Additional material
FRANCE • 73 specs; same collection data as for holotype; morphotype 2; MNHN.F. A29150, A29231, A29256, A29300 A29320 to A29322, A29326, A29328 to A29338, A29340, A29341, A29344, A29346, A29347, A29351, A29354, A29355, A29362, A29369, A29370, A53132, A53328 to A53330, A53336, A53340, A84030 to A84038 A84041, A84043 to A84058, A84060 to A84063, A84065 to A84071, R50966, R50978 • 4 specs; same collection data as for holotype; morphotype 2; MSNM i7597, i18928, i25037, i25038 • 9 specs; same collection data as for holotype; morphotype 1; MNHN.F. A29339, A29354, A29357, A29361, A53131, A84039, A84040, A84047, A84055, A84059.
Measurements
See Table 2.
Description
Shield morphology
Square-shaped to sub-trapezoidal shield in lateral view with an asymmetric anterior margin formed on a well-developed optic notch, a rounded or sharp antero-dorsal corner, a convex dorsal midline is slightly convex, with a large fin-like (Fig. 18D–E) or flat dorsal carina, a rounded postero-dorsal corner, a vertical or postero-ventrally tilted, concave posterior margin, a rounded postero-ventral corner and a ventral margin divided into a posterior half steeply descending antero-ventrally and a horizontal anterior one (Figs 16, 17A–D). Rim of all free margin delimiting a marginal fold (Fig. 16B, D).
Shield macro-ornamentation
Presence of one straight and large medio-lateral carina, running along almost the entire length of the shield and divided into two parts by a longitudinal narrow furrow (Figs 16A, C, 21A–B). Presence of seven small serrations dorsally oriented on the anterior side of the dorsal carina and of seven serrations dorsally oriented, longer than the anterior ones on the posterior side (Fig. 18D–E).
At least 13 pores forming a sinuous row in the dorsal area of the shield, above the medio-lateral-carina (Figs 16A, C, 18D–F). Horseshoe-like ornamentation or field of punctuations covering the ventral area of the shield (Fig. 19A, C, J). Fields of punctuations also covering the surface of the dorsal area (Fig. 19E–G). Punctuations in the ventral area most probably correspond to degraded horseshoe-like ornamentation.
Presence of a hump either on the medio-ventral area of the shield or near the antero-ventral corner (Figs 16A, C, 19H–J).
Sensory structures
Rounded, stalked, compound eyes protruding from the optic notch and occupying most of it (Figs 16, 18B–C). Eyes formed of hexagonal ommatidia (w = ~80 µm; l = ~80 µm; about 236 per mm²; Fig. 17F).
Cephalic appendages
Antenniform structure only perceptible by the muscle fibres protruding from the optic notch and decreasing in diameter distally (Fig. 17E).
Raptorial appendages
Presence of three pairs of slender raptorial appendages recognised by the preservation of the muscles,
protruding from the ventral margin, posterior to the presumed cephalic appendages. Raptorial appendages consisting of two parts: a proximal postero-ventrally oriented and a distal one, antero-ventrally oriented. Articulation between both parts forming an elbow.
First pair of raptorial appendages (Figs 16, 19A, C), the shortest, consisting of a proximal part with two podomeres: podomere 1 being 3.7 times as long as wide; podomere 2 being 4.7 times as long as wide and being longer than podomere 1. Distal part of the appendages formed by three podomeres: podomeres 3 being 4.4 times as long as wide; podomere 4 being 4.8 times as long as wide; podomere 5, the most distal one, being 3.1 times as long as wide.
Second pair of raptorial appendages consisting of a proximal part with two rectangular podomeres (Fig. 18M, O): podomere 1 not being well preserved; podomere 2 being 6.1 times as long as wide. Distal part of the appendage consisting of three podomeres: podomere 3 being 5.6 times as long as wide and bearing one spine on its medial side; podomere 4 being 5.2 times as long as wide and bearing three spines on its medial side; podomere 5 being 2.8 times as long as wide and ending distally in a cluster of three long spines.
Third pair of raptorial appendages, the longest, consisting of a proximal part formed by two podomeres, podomere 2 being 5.9 times as long as wide (Fig. 18I–K). Distal part consisting of three podomere: podomere 3 being 4.4 times as long as wide, bearing two spines on the distal part of its medial side; podomere 4 being 6.4 times as long as wide and bearing nine spines on its medial side, with the first four arranged in pairs; podomere 5 being 4.3 times as long as wide and ending distally with a cluster of three long spines.
Oval structure
Oval structure protruding from the ventral margin, behind the last pair of raptorial appendages (Fig. 18G– H). Structure associated with a lamellar structure in one specimen (Fig. 17G).
Posterior trunk
Nine rectangular pleural parts of trunk segments protruding from the posterior part of the ventral margin (Figs 16B, D, G, 20). In some specimens, pleural part increasing in size until tp 6, then decreasing until tp 9 (Fig. 16B, D, G). In other specimens, pleural parts decreasing in size posteriorly with last one (tp 9) thinner than the rest (Fig. 17H). Proximally, they have a postero-dorsal orientation while they are curved downward distally. Trunk ending in a square segment, i.e., the telson, bearing a rounded structure (Fig. 17I–J). Field of setae visible on the telson.
Posterior trunk appendages
Nine pairs of appendages attached to the pleural part of the posterior trunk (Fig. 20F–H). Appendages oriented postero-dorsally and proximally consisting of a curved square-shaped plate (Fig. 20H) and ending distally in a styliform part (Fig. 20I–J). Last pair of appendages with a rounded distal plate.
Gills
Eight arcuate, lamellar gills preserved below the medio-lateral carina (Fig. 19A–B).
Remarks
Paraostenia voultensis displays an important variability for some features. For instance, some specimens have a trapezoidal shield with a vertical posterior margin and a horseshoe-like ornamentation (Figs 17– 20), while others have a square-shaped shield with a postero-ventrally tilted posterior margin and no ornamentation (Fig. 16). Moreover, it seems there is a slight difference in total length (Fig. 21A): the histogram shows a bimodal distribution that might indicate the presence of two different morphotypes.
Morphometry
In order to characterise the variability of Paraostenia voultensis and to confirm the presence of two morphotypes, we ran various morphometric and statistical analyses. In this section, we consider separately both P. voultensis putative morphotypes in order to test for their differences. Morphotype 1 corresponds to the small specimens with a square-shaped shield, a postero-ventrally tilted posterior margin, and no ornamentation. Morphotype 2 corresponds to bigger specimens having a square-shaped shield with a postero-ventrally tilted posterior margin and no ornamentation.
Descriptive statistics
The measurements made on Paraostenia voultensis allow us to test the homogeneity of the sample. With the exception of the length of the shield (Ls), histograms appear normally distributed for all measurements (Fig. 21A). According to the results of the Shapiro-Wilk test (W> 0.95; p> 0.13), all measurements probably follow a normal law.
Simple allometry
For Paraostenia voultensis (Fig. 21; Table 3), a strong and significant correlation has been found for morphotype 2 (R² = 0.892, p-value <0.05) while it is non-significant for morphotype 1 (R² = 0.605, p-value = 0.222). The slope (likelihood ratio statistic equal to 0.4298, p-value = 0.5121) and the elevation (Wald statistic equal to 0.7178, p-value = 0.39687) are equal between the allometric line of both morphotypes. This indicates that there is no difference in static allometry of both morphotypes and that they are located on a similar allometric line.
For all other species, a strong and significant positive correlation has been found between shield length and shield height (R²> 0.86, p-value <0.02; Table 3).
Complex allometry
The first two principal components account for 89.0% of the variance (Fig. 22A). PC1 accounts mostly for variation in height and angle measurements while PC2 accounts mostly for variation in shield length (Supp. file 3). Size measurements appear to be correlated between them (Fig. 22B), but not with angles measurements, which also appear correlated between them.
Clustering analysis (Paraostenia voultensis)
Based on the VAT, the dataset presents a good clustering tendency that is not confirmed by the Hopkins statistic (0.57), which indicates a low clustering tendency. An optimal number of three clusters for the K-Means analysis was determined. Results of the prediction are presented in Figure 22. Cluster 1 corresponds to specimens identified as morphotype 1 while specimens identified as morphotype 2 are split between clusters 2 and 3.
description: Published as part of Laville, Thomas, Forel, Marie-Béatrice & Charbonnier, Sylvain, 2023, Re-appraisal of thylacocephalans (Euarthropoda, Thylacocephala) from the Jurassic La Voulte-sur-Rhône Lagerstätte, pp. 1-61 in European Journal of Taxonomy 898 (1) on pages 35-45, DOI: 10.5852/ejt.2023.898.2295, http://zenodo.org/record/8413500