Debruijnimys primaevus sp. nov.

Figs 3 A – O, 4 A – E, 4 I, 5 A – I, 5 M – R, 5 T, 5 U

1988 Protatera sp. Martín-Suárez, p. 145, pl. 25 a.

1991 Protatera sp. Agustí.

1993 Protatera sp. Adrover et al. p. 60, pl. 5: 11.

2003 Debruijnimys sp. Agustí and Casanovas-Vilar, p. 17, pl. 15: 7–10.

2015 Debruijnimys cf. julii Mansino et al. p. 283, pl. 5: 1.

2017 a Debruijnimys sp. Piñero et al. p. 108, pl. 5 E.

2019 Debruijnimys sp. Piñero and Agustí, p. 310, pl. 11 N – S.

2020 Debruijnimys sp. Piñero and Agustí, p. 911, pl. 5 a – d.

2023 Debruijnimys sp. Piñero et al. p. 36, pl. 7 K.

Derivation of name. From the Latin primaevus, meaning “early,” in reference to the primitive morphological features of the species.

Type materials.

Holotype. UCM-LPQ 1-N 5 B-DEB-1, isolated right m 1.

Paratypes. 15 M 1 (UCM-LPQ 1-N 1-DEB-1, UCM-LPQ 1-N 2-DEB-1 –3, UCM-LPQ 1-N 3-DEB-1; UCM-LPQ 1-N 4-DEB-1–5; UCM-LPQ 1-DER-DEB-1–5), 5 M 2 (UCM-LPQ 1-N 1-DEB-3 –5, UCM-LPQ 1-N 2-DEB-6, UCM-LPQ 1-DER-DEB-6), 1 M 3 (UCM-LPQ 1-N 2-DEB-7), 8 m 1 (UCM-LPQ 1-N 1-DEB-2, UCM-LPQ 1-N 2-DEB-4, UCM-LPQ 1-N 2-DEB-5, UCM-LPQ 1-N 4-DEB-6, UCM-LPQ 1-DER-DEB-8–11), 6 m 2 (UCM-LPQ 1-N 1-DEB-6, UCM-LPQ 1-N 1-DEB-7, UCM-LPQ 1-N 4-DEB-7, UCM-LPQ 1-DER-DEB-7, UCM-LPQ 1-DER-DEB-12, UCM-LPQ 1-DER-DEB-13), 2 m 3 (UCM-LPQ 1-N 1-DEB-8, UCM-LPQ 1-N 5 B-DEB-2).

Type locality.

La Piquera (41°25'56"N, 3°40'37"W), Duero Basin, Segovia Province, Castile and Leon, Spain (Piñero et al. 2023).

Type horizon.

La Piquera (level 5), 5.3–4.6 Ma, earliest Ruscinian, lower part of the MN 14 unit, Early Pliocene.

Diagnosis.

Small species of Debruijnimys, characterised by its small, oval anteroconid and weak connections between this cusp and the loph formed by the protoconid and the metaconid. In the m 2, a small posterolophid can be distinguished. In the M 1, a longitudinal connection between the anterocone and the protocone is present only at advanced stages of wear. In the M 2, a small anteroloph can be present, while the hypocone and metacone are differentiated cusps.

Differential diagnosis.

Debruijnimys primaevus sp. nov. differs from the type species D. julii by its smaller size (Fig. 6) and less developed longitudinal ridges in the m 1. Moreover, the oval anteroconid is smaller and does not present a labial cingulum. The connection between the anteroconid and the loph formed by the protoconid and the metaconid is weaker. The m 2 still presents a small posterolophid. In the M 1, a longitudinal connection between the anterocone and the protocone is absent, except in highly worn teeth. In the M 2, a small anteroloph is still present, while the hypocone and metacone are differentiated cusps.

Debruijnimys primaevus sp. nov. differs from Debruijnimys davidi (Geraads, 1998) by its larger size (Fig. 6). The anterocone is larger and less rounded than in D. davidi. Moreover, the anteroconid is also larger and lacks the longitudinal connection between the protoconid and the loph formed by the hypoconid and the entoconid that is present in the m 1 of D. davidi. In the M 2, the paracone and metacone are not connected, as occasionally occurs in D. davidi. The M 3 of D. primaevus sp. nov. is larger than that of D. davidi.

Debruijnimys primaevus sp. nov. differs from Protatera almenarensis Agustí, 1989 by the presence of a longitudinal ridge in the m 1 and its small, simple anteroconid. Although the size ranges overlap, P. almenarensis is, on average, slightly larger than this species (Fig. 6).

Stratigraphic and geographic range.

Early Pliocene (MN 14) of the Iberian Peninsula: La Piquera (Duero Basin); Botardo C, Botardo D (Guadix-Baza Basin); Alcoy- 4 B (Alcoi / Alcoy Basin); Puerto de la Cadena, Sifón de Librilla 413 (Fortuna Basin); La Bullana- 2 B (Cabriel Basin); La Gloria- 4 (Teruel Basin).

Measurements.

See Tables 1 – 3.

Description.

The M 1 (n = 15) presents an occlusal pattern formed by three transverse rows. The anterior one is formed by the anterocone. This cusp presents a triangular shape, the anterior wall being its widest side. In less worn teeth (Fig. 3 C, D), the anterocone appears to be formed by two independent cusps, the lingual one being larger than the labial one. The posterior walls of the anterocone are projected backwards without reaching the protocone in most cases. A second transverse row is formed by the protocone and the paracone, which are medially fused in worn specimens. In less worn teeth (Fig. 3 C, D), the two cusps are already connected, but not fused into a single row, both displaying a similar size. The third transverse row is formed by the hypocone and the metacone, the hypocone being larger than the metacone. In less worn specimens, both cusps are connected, but not fused (Fig. 3 C, D, K). Finally, in three cases, the three parallel rows are found medially connected by a longitudinal ridge (Fig. 3 F, H, I).

The M 2 (n = 5) presents an occlusal pattern formed by two transverse rows. The anterior one is formed by the protocone and the paracone. A small anteroloph attached to this anterior lobe may be present (Fig. 4 B, C). The protocone and paracone are always medially connected (Fig. 4 D, E), the two cusps becoming fused as wear advances (Fig. 4 A, B, C). The posterior lobe is formed by the hypocone and the metacone. The hypocone is larger than the metacone, the latter cusp being reduced to a smaller, rounded cusp. Both cusps are medially connected and become fused in advanced worn molars (Fig. 4 B).

The M 3 (n = 1) presents an occlusal pattern formed by a main lobe that includes the protocone and the paracone. A small, oblique cuspule can be recognised, connected to the posterior wall of the main lobe.

The m 1 (n = 9) presents an oval and asymmetric anteroconid, with no evidence of a labial spur. In unworn teeth (Fig. 5 H, I), it is still isolated, but as wear advances, its posterior wall reaches the medial part of the row formed by the protoconid and the metaconid, developing an anterior longitudinal ridge (Fig. 5 A, D, G). The protoconid and metaconid are always connected, even in unworn teeth (Fig. 5 H, I). As wear advances, they become widely confluent, forming a simple transverse ridge (Fig. 5 A, D, G). The hypoconid and entoconid are always fused, forming a simple, transverse isolated ridge. In advanced stages of wear, the posterior wall of the protoconid reaches the anterior wall of this ridge, developing a posterior longitudinal ridge. A small, rounded posterolophid is always present, which, in worn teeth, is fused to the posterior lobe (Fig. 5 E, F, G).

The m 2 (n = 6) presents a simple dental pattern formed by two lobes. The protoconid and metaconid are always fused, forming a transverse lobe. The hypoconid and entoconid are equally fused, forming a simple transverse lobe. In one tooth, a longitudinal ridge connects both transverse lobes (Fig. 5 R). In some cases, a small posterolophid can be recognised, attached to the posterior wall of this posterior lobe (Fig. 5 M, N).

The m 3 (n = 2) presents a very simple occlusal pattern formed by a single transverse lobe.

Remarks.

The oldest representatives of Debruijnimys are found at the Lissasfa site (Morocco), where Geraads (1998) described the species Protatera davidi, later transferred to the genus Debruijnimys by Agustí and Casanovas-Vilar (2003). This species differs from D. primaevus sp. nov. by its smaller size and more reduced M 3. The origin of Debruijnimys most probably lies in an archaic species of the genus Abudhabia Bruijn and Whybrow 1994, the type species A. baynunensis from the Shuwayhat Site S 4 (Baynunah Formation, Abu Dhabi; Bruijn and Whybrow (1994)) or the more derived species A. yardangensis (Munthe 1987) from the site of Sahabi (Libya; Agustí (2008)). Thus, a slight connection between the anteroconid and the protoconid is already present in the m 1 of the latter species (Agustí and Casanovas-Vilar 2003; Agustí 2008), a character that is fully developed in Debruijnimys and absent in Protatera.

At the site of Lissasfa, Debruijnimys davidi appears associated with a small mammal fauna that includes at least two European genera, Ruscinomys (R. africanus) and Prolagus (P. michauxi) (Geraads 1998; Sen et al. 2024). The presence of species of European origin in Morocco has already been described at the sites of Aïn Guettara (Apodemus aff. jeanteti, Apocricetus cf. barrierei, Eliomys truci; Brandy and Jaeger (1980)) and Argoub Kemellal (Ruscinomys cf. lasallei, Stephanomys numidicus, Castillomys africanus, Apodemus gudrunae; Coiffait et al. (1985); Coiffait-Martin (1991)). Although there is no precise dating for these African sites, it has been assumed that the entry of these European elements into Morocco was a consequence of the terrestrial pathways opened between northern Africa and the Iberian Peninsula during the MSC. Conversely, African rodents of the genus Debruijnimys also entered western Europe from northern Africa (Agustí 1989 b; Agustí and Casanovas-Vilar 2003; García-Alix et al. 2016).

After its entry into the Iberian Peninsula in the Late Miocene, Debruijnimys primaevus sp. nov. persisted into the Early Pliocene (Agustí 1991; Adrover et al. 1993; Agustí and Casanovas-Vilar 2003; Mansino et al. 2015; Piñero et al. 2017 a, 2017 b, 2023; Piñero and Agustí 2019, 2020), the last representatives of the genus (D. julii) being present in the late Early Pliocene of Asta Regia 3 (Castillo and Agustí 1996), Baza 1 (Piñero et al. 2017 b) and Gorafe 4 (Martín-Suárez 1988) (Fig. 7).