Platyscaphokogia landinii, Collareta & Lambert & Palomino & Urbina & Bianucci, 2020

Collareta, Alberto, Lambert, Olivier, Palomino, Aldo Marcelo Benites, Urbina, Mario & Bianucci, Giovanni, 2020, A new physeteroid from the late Miocene of Peru expands the diversity of extinct dwarf and pygmy sperm whales (Cetacea: Odontoceti: Kogiidae), Comptes Rendus Palevol 19 (5), pp. 79-100 : 83-84

Platyscaphokogia landinii n. sp.

( Figs 2-6; 8A)

urn:lsid:zoobank.org:act:FC3BE988-0F09-4262-911C-5B50070D1B97

ETYMOLOGY. — The specific name honours Walter Landini, Italian vertebrate palaeontologist, for his substantial contribution to the knowledge and understanding of both the Miocene vertebrate assemblages of the East Pisco Basin (e.g., Landini et al. 2017a, b, 2019) and the Italian fossil record of physeteroids (e.g., Bianucci & Landini 1999, 2006).

HOLOTYPE. — MUSM 3405 , an incomplete skull lacking the tip of the rostrum and the basicranium.

PARATYPE. — MUSM 3291, an incomplete skull, preserving only the rostrum and the right portion of the neurocranium.

TYPE LOCALITY. — The holotype was found at Cerro Hueco la Zorra, Ica desert, c. 30 km south of the town of Ica, southern coast of Peru ( Fig. 1B); geographic coordinates of the finding site: 14°26’44.35”S, 75°42’24.05”W.

TYPE HORIZON. — The holotype was found in deposits belonging to the silty upper portion of the P2 allomember of the Pisco Formation (as defined by Di Celma et al. 2017, 2018a) ( Fig. 1B, C). Stratigraphically, MUSM 3405 is located between the P2-8 and the P2-9 horizons of Di Celma et al. (2017, 2018a), which are prominent and laterally continuous ledges at the top of sheer cliff faces. At the nearby locality of Cerro Blanco, a tephra layer placed just below the P2-8 horizon has been recently dated to 7.084 ± 0.044 Ma by means of Ar-Ar radiometric analyses ( Bosio et al. 2020b). An age younger than 7.084 Ma is thus proposed for the horizon from which the holotype was collected. Considering also that no marine deposit younger than the Miocene is known from the western side of the lower Ica valley, MUSM 3405 is here regarded as Messinian (latest Miocene) in age.

LOCALITY AND HORIZON OF THE PARATYPE. — The paratype was found at Cerro los Quesos (Ica desert, c. 50 km south of the town of Ica, southern coast of Peru ( Fig. 1B, C); geographic coordinates of the finding site: 14°30’54.00”S, 75°43’08.90”W), in deposits belonging to the P2 allomember of the Pisco Formation.

MUSM 3291 was indicated with the field number O14 and identified as belonging to “aff. Scaphokogia sp. ” in the fossil map published by Bianucci et al. (2016a). The horizon from which the paratype was collected belongs to the stratal package known as “Member F” ( Di Celma et al. 2016a), within the silty upper portion of the P2 allomember; it is further located c. 35 m above a tephra layer, the Mono key bed of Di Celma et al. (2016a), that has been dated to 6.93 ± 0.09 Ma by means of Ar-Ar radiometric analyses. A stratigraphically higher volcanic ash bed, cropping out in the uppermost portion of the Cerro Los Quesos succession (i.e., 17 m above the paratype), has been dated to an age equal or older than 6.71 ± 0.02 Ma ( Di Celma et al. 2016a). As such, the horizon from which the paratype originates can be constrained to a short time interval within the Messinian, i.e., between 6.93 Ma and 6.71 Ma. Such an age estimate finds support in the biostratigraphic data, which indicate an age younger than 7.35 Ma for this portion of Member F ( Gariboldi et al. 2017).

Several fossil vertebrates from Cerro Los Quesos were found in strata belonging to Member F, including mysticetes (balaenopterids and cetotheriids), odontocetes (e.g., the holotype of the beaked whale Chavinziphius maxillocristatus , the macroraptorial stem physeteroid Acrophyseter sp. , and the phocoenid cf. Lomacetus ginsburgi ), pinnipeds, crocodiles, seabirds, and sharks ( Bianucci et al. 2016a, b; Lambert et al. 2017a).

DIFFERENTIAL DIAGNOSIS. — Platyscaphokogia landinii n. gen., n. sp. differs from Scaphokogia cochlearis by the following combination of characters: in dorsal view, skull roughly drop-shaped, due to the remarkable tapering of the rostrum towards the anterior tip of the skull; sagittal facial crest longer, less displaced laterally, dividing the supracranial basin in two different sub-basins; supracranial basin moderately shallower and slightly more anterodorsally oriented; in lateral view, rostrum vertically much thinner (i.e., dorsoventrally compressed) and not exceeding in height the lateral maxillary crests at its base; long axis of the rostrum projecting anteriorly rather than anteroventrally; in ventral view, presence of larger, well-individualised, likely functional upper dental alveoli (right maxilla presenting 10 alveoli).

DESCRIPTION, COMPARISONS, AND REMARKS

The following description is based on the holotype, unless otherwise specified.