FIRST CARBONIFEROUS PROTASPID LARVAE (TRILOBITA)

Journal of Paleontology, Jul 2005 by Lerosey-Aubril, Rudy, Feist, Raimund

Subtype "Ct" (Fig. 6.9-6.15): Characteristics.-The following features differentiate "Ct" from "Cc": α-α longer and more straight ("truncated"), posteriorly lesser convex occipital ring, αβ more diverging, anterior border only slightly curving backward abaxially, anterior part of the fixigena wider (tr.), i.e., β-β longer.

Shape changes during ontogeny.-Glabella substantially inflating; dorsal and anterior border furrows deepening; anterior border inflating; α-α lengthening; ζ migrating inwards.

No differences are observed between both subtypes in the nature of their ontogenetic changes. The timings of these latter, however, are not strictly identical.

Type D (Fig. 5.1, 5.2): Characteristics.-Glabella short (sag.); preglabellar field and anterior border especially wide (sag.); β-β particularly long. Laterally, only slightly vaulted.

Remarks.-Only three broken specimens were found.

HYPOSTOMES

Type a (Fig. 7.22-7.25): Characteristics.-Maximum width (tr.) across shoulders about 80% of maximum length; middle body poorly subdivided in anterior and posterior lobes; one to two horseshoe-shaped terrace lines on anterior lobe that open posteriorly and surround an area covered with small fragments of terrace lines; anterior wings projecting dorsolaterally; especially wide shoulders.

Shape changes during ontogeny.-Appearance of scattered terrace lines on the area surrounded by horseshoe-shaped terrace lines.

Type b (Fig. 7.26-7.29): Characteristics.-Elongate, with maximum width (tr.) across anterior wings hardly 60% of maximum length; two to three pairs of terrace lines on anterior lobe; anterior wings projecting almost exclusively dorsally; shoulders of rather moderate width (tr.); posterior border large.

Shape changes during ontogeny.-Anterior wings enlarging (exsag.); one, two, and three terrace lines successively appearing; shoulders differentiating.

LIBRIGENA

Type α (Fig. 6.16-6.27): Characteristics.-Eye absent, lateral border large with one marginal terrace line densely covered with tiny spines (Fig. 6.26); small genal spine projecting posteriorly and slightly laterally. Doublure wide and bearing three terrace lines. Librigena very high laterally. Sculpture: small tubercles, more abundant on lateral border.

Shape changes during ontogeny.-Genal field widening; lateral border furrow substantially deepening; genal spine significantly decreasing in size and projecting more and more laterally; marginal spines and tubercles decreasing in size.

Type β (Fig. 7.1-7.10): Characteristics.-Minute kidney-shaped visual surface with no obvious lenses; genal field wide; lateral border wide, slightly inflated in inner part and flattened in outer part (Fig. 7.1), with two dorsal and one marginal terrace lines; genal spine moderately flattened laterally and mainly projecting posteriorly. Test smooth.

Shape changes during ontogeny.-Differentiation of the minute visual surface; genal field expanding; lateral border, initially totally flat, inflating in its inner part.

Type γ (Fig. 7.11-7.21): Characteristics.-Eye absent; genal field particularly wide; lateral border inflated, with three terrace lines; genal spine long; doublure exceptionally large (Fig. 7.21); Librigena rather low laterally. Test smooth.