Lacazella Munier-Chalmas, 1880

Bitner, Maria Aleksandra, Lozouet, Pierre & Cahuzac, Bruno, 2013, Upper Oligocene (Chattian) brachiopod fauna from the Aquitaine Basin, southwestern France and its paleoenvironmental implications, Geodiversitas 35 (3), pp. 579-606 : 595-598

Genus Lacazella Munier-Chalmas, 1880

TYPE SPECIES. — hvecidea mediterranea Risso, 1826 , by original designation of Munier-Chalmas (1880: 279).

Lacazella mediterranea ( Risso, 1826) ( Fig. 9 A-L; Table 9)

hvecidea mediterranea Risso, 1826: 394 , pl. 12, fig. 183.

hvecidea (Lacazella) mediterranea – Peyrot 1932: 487, pl. 17, figs 7-10.

Lacazella mediterranea – Pajaud 1970: 128, text-figs 50, 52, pl. 1, fig. 4, pl. 5, fig. 4, pl. 7, fig. 3, pl. 10, figs 1-6, pl. 11, fig. 3, pl. 12, fig. 2, pl. 16. — Logan 1979: 73, text-fig. 22, pl. 10, figs 1-8. — Taddei Ruggiero 1985: 376, 377. — Álvarez & Emig 2005: 117-119, fig. 34A- C. — Bitner & Dieni 2005: 109, 110, fig. 4I-K. — Bitner & Dulai 2008: 40, fig. 5.7-8. — Dulai 2010a: 28, pl. 3, fig. 3a, b.

MATERIAL EXAMINED. — Peyrère: 306 complete specimens, 105 ventral and 72 dorsal valves, MNHN.F.A- 46537-A46543 and A46552. — Abesse: 97 complete specimens, 104 ventral and 47 dorsal valves MNHN. F.A46544-A46547, A46554 and A46556. — Estoti: four ventral valves, MNHN.F.A46548. — Bélus: one complete specimen, one ventral and one dorsal valves, MNHN.F.A46549. — Bezoye: ten complete specimens, 22 ventral and 12 dorsal valves, MNHN.F.A46550. — Escornebéou: 17 ventral valves, Larralde Collection.

OCCURRENCE. — ffle stratigraphical range of this species is from the Upper Paleocene ( Pajaud & Plaziat 1972) to Recent. Its Recent representatives are living in the south-western part of the Mediterranean Sea at the depth of 1-110 m ( Logan 2007) and are regarded as a neoendemic species ( Logan et al. 2004). It is in fact a relict distribution because in the Eocene it is recorded throughout Europe but in the Neogene it is known only from the Mediterranean region.

REMARKS fflis species dominates in the studied assemblage and is represented by more than 800 specimens. Its presence was already reported from the Oligocene of the Aquitaine Basin ( Peyrot 1932; Pajaud 1974; Lozouet 2004).

Although consistent with the hitherto described specimens (see Pajaud 1970; Logan 1979; Álvarez & Emig 2005) the specimens from southern France are much larger, reaching about 10 mm of length, thus being even three times as long as those living today, which rarely exceed 3 mm ( Logan 1979; Álvarez & Emig 2005). ffle shell is variable in outline, usually subtriangular, with large interarea and wide, triangular pseudodeltidium. ffle hemispondylium takes the form of two prominent prongs and is supported by a small median septum ( Fig. 9E ). ffle cardinal process is large and subrectangular, extending beyond the margin. ffle median septum is divided forming a trifurcating structure, and the margins of interbrachial lobes are denticulated ( Fig.9 G-L).

PALEOECOLOGICAL REMARKS ffle Brachiopoda are very abundant in the marls of Peyrère and calcareous sands of Abesse but are scarcely represented in the other five outcrops ( Fig. 1 ). From an ecological point of view the outcrops of the Upper Oligocene of the Aquitaine Basin can be divided into four main groups ( Lozouet 2004): a shallow-water calcareous facies outcropping in the vicinity of Dax (Abesse, Bezoye, Estoti), a muddy sand assemblages (Escornebéou, Bélus), a mud assemblage localized in the paleocanyon and the Peyrère fauna. ffle shallow-water calcareous facies contains numerous faunistic elements of the littoral zone indicating the proximity of the shore line; otherwise the assemblage is particularly rich in macro-fossils (molluscs, hermatypic corals, bryozoans, serpulids). ffle muddy sand assemblages are characteristic of the sublittoral zone up to the depth of 80 m as indicated by the presence of gastropods with bathyal habitats: Seguenziidae Verrill, 1884 , Benthonella Dall, 1889 , Benthonellania Lozouet, 1990 ( Lozouet 1990) .ffle mud assemblages correspond to the distal part of the shelf and the top of the continental slope. ffle Peyrère fauna deserves special explanation. ffle originality of the Peyrère associated fauna, including gastropods, bivalves, annelids, corals with a very common species of the genus Epiphaxum Lonsdale, 1850 (Octocorallia) ( Lozouet & Molodtsova 2008), is clearly in abundance of elements characteristic for hard substrates and cryptic habitats ( Lozouet 2004). Otherwise there are very characteristic forms, restricted today only to the submarine cave environments. ffle gastropod families Neritopsidae Gray, 1847 , Neritiliidae Schepman, 1908 and Pickworthiidae Iredale, 1917 are the most emblematic. ffle micromorphic megathyridid and thecideide brachiopods commonly occur together, both today and in the fossil record ( Meile & Pajaud 1971), in shallow-water, tropical and subtropical environments ( Logan 2005, 2008; Lüter et al. 2008).ffle thecideides display the greatest density in light-poor, cryptic habitats as overhangs, crevices, caves and subreef tunnels ( Lee & Robinson 2003; Logan 2004). fflus, their abundance in the Peyrère assemblage supports the earlier interpretations of the whole fauna as a cave biocenosis. In turn, the protected, stable environments of cryptic habitats may explain much larger size of Lacazella mediterranea from Peyrère than hitherto reported for this species.

DRILLING PREDATION

Gastropod predation intensity, with only few exceptions (see e.g., Baumiller & Bitner 2004; Baumiller et al. 2006), is usually very low in most Cenozoic brachiopod populations ( Taddei Ruggiero & Bitner 2008), as here. Among 1466 specimens examined 59 specimens (4.0%) were drilled (see Table 10). Such a low frequency may be explained by the fact that brachiopods are not the prime target where molluscs are very abundant. Drillings were observed on Terebratulina retusa , Megathiris detruncata , Joania cordata , J. peyrerensis n. sp. and Lacazella mediterranea . No drilling predation was observed on Novocrania anomala , Argyrotheca cuneata , A. bitnerae or Megerlia truncata . Taxonomic selectivity for particular species is difficult to explain and does not depend on amount of specimens. Drill holes were found on ventral and dorsal valves but the dorsal valve was drilled at a higher frequency (see Table 10); in two specimens drill holes occur on both valves ( Fig. 10 ).

Drill holes on calcareous exoskeletons are for the most part due to two families of gastropods: Naticidae Guilding, 1834 and Muricidae Rafinesque, 1815 ( Carriker & Yochelson 1968). Drilling predation is known also in the scavenger family Nassariidae Iredale, 1916 (but it is exceptional) and in the Cassidae Latreille, 1825 , which feed exclusively upon echinoderms ( Riedel 1995). Naticidae and Muricidae are widespread in the Upper Oligocene of the Aquitaine Basin but the Naticidae are less common, being infaunal gastropods more common in littoral sandy deposits. In the outcrop of Peyrère where the Brachiopoda are especially common and very well preserved a bulk sample has permitted us to obtain 413 species of gastropods ( Lozouet 2004) including two species of Naticidae (36 specimens) and 19 species of Muricidae (133 specimens). ffle Muricidae generally feed upon sedentary epifaunal prey and the Naticidae only bore when the prey is buried in sediment.

It is possible to differentiate boreholes produced by Muricidae or by Naticidae based on morphological criteria. ffle bore hole of Naticidae is neat and circular with a wide conical shape while those of Muricidae are more irregular; the hole is also straight-sided, or tapers slightly inwards ( Taylor 1970). ffle holes reported in the studied brachiopod shells correspond clearly to muricid attacks ( Fig. 10A , D-L). fflis is in good agreement with ecology of brachiopods and muricids, and diversity of muricids in the Peyrère outcrop.

Figures

FIG. 9. — Lacazella mediterranea (Risso, 1826), Upper Oligocene: A-C, dorsal views of complete specimens: A, C, Peyrère, MNHN.F.A46537-A46538; B, Abesse, MNHN.F.A46544; D, E, inner view of ventral valve and tilted enlargement (E) to show hemispondylium, Abesse, MNHN.F.A46545; F, inner view of ventral valve, Peyrère, MNHN.F.A46539; G, inner view of dorsal valve, Abesse, MNHN.F.A46546; H, I, inner and posterior views of dorsal valve, Peyrère, MNHN.F.A46540; J, inner view of dorsal valve, Peyrère, MNHN.F.A46541; K, L, inner view of dorsal valve and enlargement (L) of the trifurcating median ramus-ramuli complex, Peyrère, MNHN.F.A46542. All SEM. Scale bars: A, B, D, E, G-I, L, 1 mm; C, F, J, K, 2 mm.

FIG. 1. — Map of the Aquitaine Basin, SW France showing the extension of the Chattian marine deposits (dotted line) and the localities of brachiopod fauna; heavy lines denote anticlinal ridges (simplified after Cahuzac et al. 1995).

FIG. 10.— Examples of drilled brachiopods from the Upper Oligocene of the Aquitaine Basin,SW France:A, Joania cordata (Risso,1826),ventral valve,Abesse,MNHN.F.A46551;B,C, Megathirisdetruncata(Gmelin,1791),ventralvalve and a close-upimage of drillhole,Bélus,MNHN.F.A46506; D, E, Lacazella mediterranea (Risso,1826),ventral valve and close-up of drill hole,Peyrère,MNHN.F.A46552;F, G, M. detruncata, dorsal valve and close-up of drill hole, Peyrère, MNHN.F.A46554; H, I, L. mediterranea, dorsal valve and close-up of drill hole, Abesse, MNHN.F.A46553; J, Terebratulina retusa (Linnaeus, 1758), dorsal valve, Peyrère, MNHN.F.A46555; K, L, L. mediterranea, dorsal view of complete specimen and a close-up image of drill hole,Abesse,MNHN.F.A46556.All SEM.Scale bars:A,I, L, 500 µm;B-D,G, H, J, K, 1 mm; E, 200 µm; F,2 mm.