Leptochiton lignatilis, Dell'Angelo, Bertolaso & Sosso, 2015
|
publication ID |
https://doi.org/ 10.26879/552 |
|
publication LSID |
lsid:zoobank.org:pub:17950F77-D49D-4D22-A0FD-77240FD36070 |
|
persistent identifier |
https://treatment.plazi.org/id/29F12828-2C47-402C-AE6D-08CB47432214 |
|
taxon LSID |
lsid:zoobank.org:act:29F12828-2C47-402C-AE6D-08CB47432214 |
|
treatment provided by |
Felipe |
|
scientific name |
Leptochiton lignatilis |
| status |
sp. nov. |
Leptochiton lignatilis View in CoL n. sp. Dell’Angelo, Bertolaso and Sosso
Figures 2-4 View FIGURE 2 View FIGURE 3 View FIGURE 4
zoobank.org/ 29F12828-2C47-402C-AE6D-08CB47432214
Type material. Holotype: MGPT-PU 108787 (tail valve, Figure 2.1-4 View FIGURE 2 View FIGURE 3 View FIGURE 4 ); paratypes: MGPT-PU 108788 (head valve, Figure 2.6 View FIGURE 2 -7); MZB 32033 View Materials (intermediate valve, Figure 3.1-2 View FIGURE 3 , broken during preparation for SEM); MZB 32034 View Materials (intermediate valve); NHMW 2014 View Materials /0451/0001 (intermediate valve, Figure 3.3-4 View FIGURE 3 View FIGURE 4 ); NHMW 2014 View Materials /0451/0002 (tail valve, Figure 2.5 View FIGURE 2 ); ZISP 2226 View Materials (intermediate valve); ZISP 2227 View Materials (intermediate valve); MSNG 57980 View Materials (one intermediate and one head valve); MZPD MAL-2074 (intermediate valve, Figure 2.8 View FIGURE 2 -9); MZPD MAL-2075 (head valve). MZPD MAL-2076 (fragment of intermediate valve, Figure 3.5 View FIGURE 3 -8). These valves are from the Tortonian of Torrente Cinghio , Parma, Emilia Romagna, N Italy. Another paratype, MZPD MAL-2077 (fragment of intermediate valve, Figure 4.1- 2 View FIGURE 4 ), is from the Langhian of Moncasale di Casina, Reggio Emilia, Emilia Romagna.
Other material examined. 100 valves, most of them incomplete, from the Tortonian of Torrente Cinghio, in BD and LB.
Type locality. Torrente Cinghio , Parma , Italy; Miocene, Tortonian .
Type horizon. Dark grey claystone of the Termina Formation, Tortonian in age.
Etymology. The name lignatilis (relating to the wood) is from the Latin lignum (wood), with referring to the substrate linked to this species.
Distribution. Leptochiton lignatilis n. sp. is only known from the Miocene of northern Italy, particularly from the Tortonian of Torrente Cinghio (Parma), and from the Langhian of Moncasale di Casina (Reggio Emilia).
Diagnosis. Head valve semioval; intermediate valve rectangular, carinated, elevated; tail valve more than semicircular, mucro anterior. Tegmentum ornamented by irregularly arranged, well-separated roundish-subquadrangular granules.
Description. Holotype width (lateral) 3.5 mm, length (antero-posterior) 2.5 mm; maximum width 2.4 / 3.4 / 3.5 mm (head, intermediate, and tail). Head valve semioval ( Figure 2.6 View FIGURE 2 ), posterior margin widely V-shaped, slope concave. Intermediate valve broadly rectangular ( Figure 3.1 View FIGURE 3 ) with slightly rounded corners, carinated, anterior and posterior margins almost straight, apex indistinct, elevated (height/width 0.5), lateral areas scarcely differentiated. Tail valve more than semicircular ( Figure 2.1 View FIGURE 2 ), anterior margin convex, mucro anterior, not prominent, antemucronal slope convex, postmucronal slope a little concave just underneath mucro.
Sculpture of tegmentum formed by rather irregular elevated granules, of roundish shape ( Figure 2.7 View FIGURE 2 ), well separated from each other, irregularly arranged, except apex portion of head valve with concentric ridges. Granules become more irregularly elongate ( Figure 3.5 View FIGURE 3 -6) towards the jugal area of intermediate valves, but always well separated, not coalescing. Each granule (diameter 40 to 50 μm) bears a more or less central macroaesthete, and variable number of microaesthetes, two to four, up to five to six in more elongate granules ( Figures 2.9 View FIGURE 2 , 3.6 View FIGURE 3 ). Elongate granules can reach a maximum length up to 70 μm.
Articulamentum without insertion laminae ( Figure 2.2 View FIGURE 2 ). Apophyses small, triangular in intermediate valves ( Figure 3.1, 3.3 View FIGURE 3 ), more or less trapezoidal in tail ones ( Figure 2.1, 2.3 View FIGURE 2 ), widely separated by a large jugal sinus.
Remarks. In the material studied there are almost only small fragments of valves (of about 1-1.5 mm or less of width). Even though these fragmented valves have clearly visible tegmentum granules, in many cases it is not possible to identify them as head, intermediate or tail valves. Only 15 valves are complete or sufficiently complete.
The small fragment of the intermediate valve from Moncasale di Casina ( Figure 4 View FIGURE 4 ) has a sculpturing matching that of the material from Torrente Cinghio and is compatible with an attribution as Leptochiton . Considering the similarities of the sculpture, we provisionally consider this valve conspecific with the material from Torrente Cinghio.
Comparisons. The sculpture of Leptochiton ’s tegmentum is fundamentally of two types, fully covered with randomly or quincuncially arranged granules, or with granules arranged in longitudinal striae in central and antemucronal areas (and both randomly/quincuncially or in radial striae on head valve, lateral and postmucronal areas).
For Leptochiton species known from sunken woods ( Sigwart and Sirenko, 2012, table 2), 12 of 23 have a tegmental sculpture that is comparable with Leptochiton lignatilis n. sp. Five of them are less elevated, with a different shape of the tail valve and a subcentral mucro: Leptochiton angustidens Sigwart and Sirenko, 2012 , L. consimilis Sigwart and Sirenko, 2012 , L. schwabei Sigwart and Sirenko, 2012 , L. deforgesi Sirenko, 2001 and L. vanbellei Sirenko, 2001 (the latter with a slightly anterior mucro). Six others are also less elevated and also have a different shape of the tail valves and have a subcentral mucro, but they also differ in having the granules in the central areas more or less arranged in distinctive longitudinal rows: Leptochiton benthedi ( Leloup, 1981) , L. rogeri Sigwart and Sirenko, 2015 (new name for L. clarki Sigwart and Sirenko, 2012 , see Sigwart and Sirenko, 2015), L. longisetosus Sigwart and Sirenko, 2012 , L. thandari Sirenko, 2001 , L. vitjazi ( Sirenko, 1977) and L. boucheti Sirenko, 2001 (the latter with a slightly anterior mucro).
Leptochiton kurnilatus Kaas, 1985 is a carinated and elevated species comparable with L. lignatils n. sp. (height/width 0. 57 vs. 0.5), but differs by the different shape and profile of tail valves, with the posterior mucro at about three quarters of the valve length.
Only three Leptochiton species from the Mediterranean Neogene have the same kind of tegmental sculpture, fully covered with randomly or quincuncially arranged granules. Leptochiton tavianii Dell'Angelo et al., 2004 from the Pliocene of Estepona ( Spain) differs in having the granules characterized by a fungiform section and arranged in a beehive structure; L. salicensis Dell'Angelo and Bonfitto, 2005 from the Pleistocene of Salice (South Italy) has sturdier yet dissimilar valves, which are evenly rounded (subcarinated in L. lignatilis ), a less elevated tail valve with a subcentral mucro (anterior in L. lignatilis ) and more polygonal granules. The Pliocene-recent Leptochiton alveolus (M. Sars in Lovén, 1846) is characterized by the tegmentum covered with pronounced, neatly separated, rounded to oval granules, more or less distinctly quincuncially arranged on all the valves surface, the lateral areas indiscernible from the central areas and arched intermediate valves (see Kaas, 1981 for a detailed description). This deep-water chiton, and secondarily the distinct Leptochiton belknapi Dall, 1878 ( Wu and Okutani, 1984), are the most comparable species to L. lignatils n. sp. Differences between these species are summarized in Table 1. The specimen reported as “ L. alveolus ” from Eocene-Oligocene cold-seep limestones of the Olympic Peninsula, Washington ( Goedert and Campbell, 1995; Squires and Goedert, 1995; Peckmann et al., 2002) has not been considered for this comparison because its specific and even generic assignment remains an open problem ( Schwabe and Sellanes, 2010). However, geographic and stratigraphic separation of this specimen from L. lignatils n. sp. allows considering them as different species.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.