Figure 1.
Panoramic view of the highest level of exploitation in Owadów-Brzezinki Quarry (i.e. unit III and most fossiliferous ‘Corbulomima horizon’ occurring in the middle of the quarry wall) and locality map.
Key: 1, Marine sediments, not studied in detail. 2, Shallow water limestone. 3, Siliclastic, fine grained sediments.
Figure 2.
Three-dimensionally preserved representatives of Late Jurassic Limulus darwini that can be assigned to three major size classes.
(a) compressed and incomplete prosoma (ZPAL X.1/O-B/XA 5); (b) Markedly incomplete prosoma (ZPAL X.1/O-B/XA 4); (c) slightly incomplete opisthosoma (ZPAL X.1/O-B/XA 6); (d) small, incomplete opisthosoma (ZPAL X.1/O-B/XA 7); (e), (f) Positive (rock slab with imprint) and negative (external mould) of the holotype (ZPAL X.1/O-B/XA 1), preserved as slightly compressed and juxtapositioned prosoma and opisthosoma; (g–i) least-deformed specimen (ZPAL X.1/O-B/XA 2), preserved as a near-complete, medium-sized prosoma; (j–l) flattened, complete prosoma (ZPAL X.1/O-B/XA 3), with exceptionally well-preserved right compound eye.
Figure 3.
Comparison of modern Limulus polyphemus (left) and oldest known member of the genus Limulus darwini (right) from Corbulomima horizon of unit III from Late Jurassic (upper Tithonian = Middle Volgian) sedimentary sequence at Owadów-Brzezinki Quarry (central Poland).
(X), (Y) and (Z) - details emphasized, are most substantial morphological difference between both these forms. (cl) - cardiac lobe; (opr) – opisthosomal rim; (pa) – posterial area. Morphological elements of L. darwini exoskeleton not known from the fossil record (i.e. movable spines and telson) emphasized in grey.
Table 1.
Table of biometric measurements of selected specimens Limulus darwini sp. nov.
Figure 4.
Graphical expression of the concept of stabilomorphism.
Evident (D–G) and potential (C and H) stabilomorphs (i.e. organisms not extending the genus level, with very slow rate of evolutionary speciation). The proposed degree of stabilomorphism (1–5) is consistent with a five-step scale of the greatest mass extinctions in the history of life (I–V) (sensu [95]). Note that two genera (A and B), previously recognized as a model example of living fossils would thereby lose their present status (see explanations in text). Information about the stratigraphic ranges of stabilomorphs were taken from: (A) – [116]; (B) – [117]; (C) – [118]; (D) – data presented here; (E) – [119]; (F) – [120] and [121]; (G) – [122]; (H) – [123].