Mucropetraliella marielou, Martha & Scholz, 2025

Mucropetraliella marielou sp. nov.

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( Fig. 17.1–6 View FIGURE 17 )

Material examined. Holotype: SMF 1825 About SMF (St. 283 KU; Fig. 17.1–2, 17.6 View FIGURE 17 ) . Paratypes: SMF 1804 About SMF ( 2 specimens; St. 236 KD; A = Fig. 17.3 View FIGURE 17 , B = 17.3–4) , SMF 40791 About SMF (St. 283 KU; Fig. 17.5 View FIGURE 17 ) .

Etymology. The species is named in honour of Marie-Louise Tritz, technical assistant at the Senckenberg Research Institute, for her invaluable work during so many SEM sessions.

Description. Colonies encrusting, multiserial, unilamellar ( Fig. 17.1 View FIGURE 17 ). Zooids arranged quincuncially, separated by salient rims. Pore chambers not observed. Ancestrula autozooidal, budding three autozooids distally and laterally ( Fig. 17.2 View FIGURE 17 ).

Autozooids irregularly polygonal to subrectangular, 717–1251 μm (ẋ = 923 ± 109 µm; CV = 12; N = 51 on 4 specimens) long by 397–885 μm (ẋ = 601 ± 116 µm; CV = 19; N = 51 on 4 specimens) wide ( Fig. 17.3 View FIGURE 17 ). Frontal shield convex, strongly raised around mucro, evenly pierced by> 70 circular pores. Orifice transversely elliptical, obscured by mucro proximally; condyles and lyrula not observed in material examined ( Fig. 17.3 View FIGURE 17 ). Mucro suboral, projecting outwardly, pointing, often broken and incompletely preserved ( Fig. 17.4 View FIGURE 17 ). Secondary orifice roundedrectangular, 168–294 μm (ẋ = 231 ± 27 µm; CV = 12; N = 29 on 4 specimens) long by 229–330 μm (ẋ = 289 ± 25 µm; CV = 9; N = 29 on 4 specimens) wide ( Fig. 17.5 View FIGURE 17 ). Spine bases absent. Ovicells hyperstomial, globular, 346–381 μm (ẋ = 365 ± 15 µm; CV = 4; N = 4 on 1 specimen) long by 407–471 μm (ẋ = 445 ± 27 µm; CV = 6; N = 4 on 1 specimen) wide; ectooecia densely pierced by tiny, circular pores ( Fig. 17.6 View FIGURE 17 ) .

Avicularia monomorphic, adventitious, single or paired, located lateral to the secondary orifice, bilaterally symmetrical, longitudinally elliptical, 92–136 μm (ẋ = 108 ± 10 µm; CV = 9; N = 39 on 4 specimens) long by 59–105 μm (ẋ = 82 ± 11 µm; CV = 13; N = 39 on 4 specimens) wide ( Fig. 17.4–6 View FIGURE 17 ). Avicularian aperture centrally located, longitudinally elliptical, occupying most of avicularian frontal; crossbar complete, at about half the avicularian length. Rostrum rounded, strongly elevated, proximolaterally directed. No other avicularia observed in studied material .

Kenozooids not observed.

Remarks. Mucropetraliella marielou sp. nov. has an unbranched mucro, and the species lacks oral spine bases ( Fig. 17.4 View FIGURE 17 ), which are common in many species currently assigned to the genus. For example, the widespread species Mucropetraliella thenardii Audouin, 1826 , has a complex, branched mucro that is associated with avicularia (see figures in Harmelin 2014). The latter species has been described from the northern Red Sea ( Balavoine, 1959) and was mentioned in a faunal list from the Sudanese coast ( Dumont 1981, p. 635). It has become a widely reported species from the northwestern Indian Ocean, and was later found along the coasts of the southeastern Mediterranean Sea ( Harmelin 2014).

On the other hand, Mucropetraliella ellerii ( MacGillivray, 1869) , type species of the genus, from the coasts off Victoria, Australia, has a small, unbranched mucro, which more closely resembles the mucro in Mucropetraliella marielou sp. nov., and likewise lacks oral spine bases. However, the mucro in Mucropetraliella ellerii is infrequently associated with a large, proximolateral avicularium ( Bock 1982, fig. 9.16a; Sanjay et al. 2024b, fig. 8), thus differing from our new species, in which avicularia are found only lateral to the orifice ( Fig. 17.5 View FIGURE 17 ), but never on the frontal shield proximolateral to the mucro.

Other species described from the northwestern realm of the Indian Ocean include Mucropetraliella stemmatum Sanjay, Venkatraman, Shrinivaasu & Louis, 2024 , and Mucropetraliella philippinensis ( Canu & Bassler, 1929) from the waters around southern India, and Mucropetraliella laccadivensis ( Robertson, 1921) from the Lakshadweep Sea. Mucropetraliella stemmatum has a tripartite mucro associated with avicularia that is comparable to that in Mucropetraliella thenardii . Mucropetraliella philippinensis was first recorded from Indian waters by Menon & Nair (1967) and imaged by Sanjay et al. (2024b). It has oral spines and a large adventitious avicularium proximolateral to the unbranched mucro. Mucropetraliella laccadivensis has never been reimaged since its first description. Judging from the original drawing provided by Robertson (1921) it may be synonymous with Mucropetraliella thenardii , as it has a tripartite mucro and large adventitious avicularia proximolateral to the mucro.

Another notable species is Mucropetraliella malwanensis Sonar, Wayal & Badve, 2021 from Quaternary deposits of Akshi and other localities along the Konkan Coast, Maharashtra, India. This species most closely resembles Mucropetraliella marielou sp. nov. as it has a short, unbranched mucro and paired avicularia lateral to the orifice. However, the avicularia in Mucropetraliella malwanensis are usually much smaller and only occasionally enlarged. Furthermore, they may occur occasionally in other positions on the frontal shield and the mucro often bears a short medial avicularium.