Spongilla patagonica Volkmer-Ribeiro and Reitner, 1991

Pronzato, Roberto, Pisera, Andrzej & Manconi, Renata, 2017, Fossil freshwater sponges: Taxonomy, geographic distribution, and critical review, Acta Palaeontologica Polonica 62 (3), pp. 467-495 : 479-481

Spongilla patagonica Volkmer-Ribeiro and Reitner, 1991

Fig. 13.

Type horizon: Aptian , Lower Cretaceous .

Type locality: 16 km NNW of Cerro Condor, Patagonia , Chubut River Valley, Argentina .

References: Volkmer-Ribeiro and Reitner 1991; Manconi and Pronzato 2002.

Description (emended from Volkmer-Ribeiro and Reitner 1991).—Megascleres oxeas (210–260 × 7–10 μm), slim, smooth, gradually sharply pointed, slightly curved. Microscleres oxeas (100–110 × 9–10 μm) spiny, usually straight to

→ Fig. 11. Eospongilla morrisonensis Dunagan, 1999 , Spongillida : Spongillidae ; Morrison Formation, Upper Jurassic, Fort Collins, Colorado, USA. A. Holotype USNM 496326; A 2, enlargement of the central area of A 1 showing straight oxeas and slightly curved strongyles. B–D. Paratype USNM 496327. B. Longitudinal section showing arcuate distribution of spicules around the perimeter. C. Spicule bundle (large clear area). D. Longitudinal and transverse sections of oxeas. E. Longitudinal section of strongyle. F. Longitudinal section of oxeas (note recrystallized texture of spicules). Modified from ( Dunagan 1999).

A

B 2 mm C

E 250 μm F

200 μm D 50 μm

500 μm G 100 μm

A 1 mm B 500 μm

E 100 μm F 100 μm

C

G

200 μm D 100 μm

30 μm H 30 μm

slightly curved. Gemmuloscleres strongyles (70–80 × 8 μm) strongly spiny, short, cylindrical, slightly to strongly bent, rarely straight with some larger and curved spines at the star-like tip. Gemmules subspherical (470 μm in diameter) with thick inner layer (20 μm) and thick pneumatic layer (100 μm). Gemmuloscleres randomly oriented and loosely packed in the gemmular theca, with tips protruding in places. Foramen single, nipple-like.

Remarks.— Spongilla patagonica was erected by Volkmer-Ribeiro and Reitner (1991), offering reasonable taphonomical explanation, within the framework of the re-description of P. chubutensis (partim). Subsequently, the species was considered invalid by Manconi and Pronzato (2002). The presumed spicular mixture and overgrowing of two sponge species, perfectly preserved and retaining even the eggs (or so interpreted), was based on previous descriptions on the presence of two gemmular morpha, i.e., unarmed and armed. Both skeleton spicules and the two gemmular types of S. patagonica were ascribed to P. chubutensis in the 1975 paper of Racek and Harrison. Moreover, Volkmer-Ribeiro and Reitner (1991) did not clearly discriminate between specimens and spicular complement descriptions of the two species. Thus this case could be solved with additional material and studies. In any case the complex P. chubutensis and S. patagonica shows that in the Early Cretaceous the freshwater sponge gemmule architecture was virtually identical to that of the more complex gemmules of Recent species, denoting a very early conservative evolutionary trend with no subsequent major functional changes.