Paraethomys baeticus, Piñero & Verzi, 2020

Piñero, Pedro & Verzi, Diego H., 2020, A new early Pliocene murine rodent from the Iberian Peninsula and its biostratigraphic implications, Acta Palaeontologica Polonica 65 (4), pp. 719-731 : 721-725

Paraethomys baeticus sp. nov.

Fig. 3 ; SOM 2: figs. S1, S2.

ZooBank LSID: urn:lsid:zoobank.org:act:469E1CBA-4E2F-45BD-8900-0A1F804C0F5A

1974 Paraethomys sp. 1 ; De Bruijn 1974: 438: pl. 2: 7; text-figs. 1, 3. 1984 Paraethomys meini ( Michaux, 1969) ; Agustí and Martín-Suárez

1984: 277.

1984 Paraethomys cf. meini ( Michaux, 1969) ; Ruiz Bustos et al. 1984: 236, pl. 2: 7, 8.

1988 Paraethomys meini ( Michaux, 1969) ; Martín-Suárez 1988: 80, pl. 1: 14.

1993 Paraethomys anomalus Bruijn, Dawson, and Mein, 1970 ; Adrov- er et al. 1993: 74, pl. 11: 1–5.

2008 Paraethomys aff. abaigari Adrover, Mein, and Moissenet, 1988 ; García-Alix et al. 2008a: 195, pl. 3: AE–AJ.

2013 Paraethomys aff. abaigari Adrover, Mein, and Moissenet, 1988 ; Mansino et al. 2013: 271, pl. 3: 18–23.

2015 Paraethomys aff. abaigari Adrover, Mein, and Moissenet, 1988 ; Mansino et al. 2015a: 560, pl. 3: E–I.

2015 Paraethomys aff. abaigari Adrover, Mein, and Moissenet, 1988 ; Mansino et al. 2015b: 280, pl. 3: 18–22.

2017 Paraethomys aff. abaigari Adrover, Mein, and Moissenet, 1988 ; Piñero et al. 2017a: e1338294-9, pl. 5: M–R.

2019 Paraethomys aff. abaigari Adrover, Mein, and Moissenet, 1988 ; Piñero and Agustí 2019: 308, pl. 11: I–M, pl. 12: F, M.

Etymology: From Latin masculine adjective baeticus [ba.e’ti.cus], in reference to the Roman province Baetica, partially corresponding to modern Andalusia, the place of the type locality.

Type material: Holotype: BA1-2001- R7 /2, isolated left M1 . Paratypes: 25 M1 (BA1-2001- R7 /1, BA1-2001- R7 /3–16, BA1-2018- R1 /1–5, IPS 89269, IPS89270, IPS89272, IPS89273, IPS89274), 28 M2 (BA1- 2001- R7 /17–31, BA1-2018- R1 /6, IPS89275–89286), 12 M3 (BA1- 2001- R8 /17–20, BA1-2018- R1 /8, IPHES-Bz-1- R8 /22, IPS89287, IPS89288, IPS89292–89295), 37 m 1 (BA1-2001- R7 /32–54, BA1- 2018- R1 /9–12, IPS8297–82306), 44 m 2 (BA1-2001- R7 /55–81, BA1- 2018- R1 /13–16, BA1-2018- R1 /18, IPS89308–89319), 27 m 3 (BA1- 2001- R8 /1–16, BA1-2001- R8 /21, BA1-2018- R1 /19–21, IPS89320, IPS89323, IPS89325–89329). All from type locality and horizon .

Type locality: Baza-1 (37º29’00”N and 2º47’05”W), Guadix-Baza Basin, Granada Province, Andalusia, Spain ( Piñero et al. 2017a; Ros-Montoya et al. 2017).

Type horizon: Paraethomys baeticus Zone (previously referred as Paraethomys aff. abaigari Zone by Piñero et al. 2018), 4.6–4.3 Ma, Baza Formation, early Ruscinian, early Pliocene.

Diagnosis.—Medium-sized species of Paraethomys with marked longitudinal connections both in upper and lower molars, but incomplete stephanodonty. Teeth intermediate in size between the small-sized Paraethomys meini and the large-sized Paraethomys abaigari and Paraethomys jaegeri . M1 and, to a lesser extent, M2 with posterior spurs on t1 and t3 directed towards the t4–t5 and t5–t6 intersections, respectively. M1 with high t6–t9 and low t4–t8 connections and small t12. t9 and t12 absent in M2. Regular presence of a funnel between the anteroconid and the protoconid-metaconid in m1, as well as absent or greatly reduced tma, moderate labial cingulum with large posterior accessory cuspid, and longitudinal spur.

Paraethomys baeticus sp. nov. differs from Paraethomys meini in: larger size ( Fig. 4 ); M1 with higher frequency of distal spurs on t1 and t3, somewhat stronger connection between t6 and t9, and mostly smaller t12; complete absence of t9 on M2; higher frequency of occurrence of longitudinal spur on m1. Differences with Paraethomys abaigari are mainly biometrical, P. baeticus sp. nov. being on average smaller than P. abaigari ( Fig. 4 ). Distinct from Paraethomys jaegeri in: smaller size ( Fig. 4 ); molars relatively narrower; M1 and M2 with less developed distal spurs on t1 and t3. Distinguishable from Paraethomys belmezensis in: better developed connections among cusps in the molars; M1 with t6 connected to the t9; larger t3 on M2; m1 with absent or greatly reduced tma. Differing from Paraethomys balearicus in: lower-crowned molars; complete absence of t9, and t1 and t3 never connected on M2; complete absence of a funnel between the posterior accessory cuspid and hypoconid, and lower accessory labial cuspids on m1. Distinct from Paraethomys lissasfensis Geraads, 1998 in: larger size; M1 with high t2–t3 connection.

Measurements.—See Table 1 and SOM 1: table S1.

Description.— Paraethomys baeticus sp. nov. from Baza-1 was first described in detail by Piñero et al. (2017a), who referred it as Paraethomys aff. abaigari . Subsequent sampling in that site has made it possible to enlarge the original sample attributable to that species. On the basis of the original and new teeth we emend the description as follows:

The M 1 (n = 26) is antero-posteriorly elongate, wider posteriorly than anteriorly. The t1 is somewhat displaced backwards with respect to the t3. The union between t2 and t3 is higher than the union between t1 and t2. There is neither a t1bis nor a t2bis. A round and low extra cusp between the t2 and t3 is present in one specimen (BA1-2001- R7 /15; SOM 2: fig. S1D). All the teeth have a distal spur on the t1 connected basally to the t4–t5 intersection. A distal spur on t3 directed to the t5–t6 intersection is also present. It lies on the valley between the t5 and t 6 in eight out of 25 cases in which this part of the tooth is well preserved (BA1-2001- R7 /1, BA1-2001- R7 /5, BA1-2001- R7 /11, BA1-2001- R7 /15, BA1- 2018- R1 /1, BA1-2018- R1 /2, IPS89272, IPS89273; Fig. 3B ; SOM 2: fig. S1D, E, J, K, L). The t4–t6, t9, t8 are united, the connection between t4 and t8 being much lower than the rest. The t6–t9 connection is high. There is a small or medium-sized t 12 in all the specimens. There are three major roots (one anterior, one posterior and one lingual) .

The M 2 (n = 28) has a nearly rounded occlusal outline, expanded anteriorly and narrower and rounder posteriorly. It has a large, oval or comma-shaped t1. A low posterior spur on the t1 directed towards the t4–t5 intersection is present in 20 out of 28 specimens ( Fig. 3E ), and absent in the remaining eight (BA1-2001- R7 /19, BA1-2001- R7 /21, BA1-2001- R7 /22, BA1-2001- R7 /25, BA1-2001- R7 /26, IPS89278, IPS89280, IPS89285; Fig. 3D, F ). The small, isolated t3 can be rounded or comma-shaped. It develops a reduced distal spur directed to the t5–t6 intersection in seven out of 28 individuals (BA1-2001- R7 /20, BA1-2001- R7 /25, BA1-2001- R7 /30, BA1- 2018- R1 /6, IPS89276, IPS89279, IPS89284; see Fig. 3F ; SOM 2: fig. S1 R, T, Y). The t9 is reduced to a crest connecting t6 and t8. It is slightly inflated only in 14% of specimens (BA1-2001- R7 /21, BA1-2001- R7 /22, IPS89276, IPS89281; see Fig. 3D ; SOM 2: fig. S1U, V). The t4–t5 connection is weak and low. The t4 is connected basally to t8. The t12 is absent. There are three roots (anterior, posterior, and lingual) .

In occlusal view, the M3 (n = 12) is subtriangular. The large t1 is isolated. The t3 is absent. The t4–t6, t8 are connected forming a central depression (see Fig. 3G, H ). This depression is generally closed, but it is open lingually between t4 and t 8 in four specimens (BA1-2001- R8 /22, BA1- 2018- R1 /8, IPS89292, IPS89293; SOM 2: fig. S1AB, AD), and open labially between t6 and t 8 in three other teeth (BA1-2001- R8 /20, IPS89287, IPS89295; see Fig. 3G ; SOM 2: fig. S1 AC, AF). Three roots are present (anterior, posterior, and lingual) .

The m1 (n = 37) is broader posteriorly than anteriorly. The lingual anteroconid is slightly more anteriorly extended than the labial anteroconid. The protoconid and hypoconid are somewhat displaced posteriorly with respect to the metaconid and entoconid. The tma is absent in 29 specimens ( Fig. 3L, P ), and greatly reduced and low in the remaining six (BA1-2001- R7 /32, BA1-2001- R7 /36, BA1-2001- R7 /38, BA1-2001- R7 /46, BA1-2018- R1 /12, IPS89304; see Fig. 3I and SOM 2: fig. S2B). A round islet of enamel between the anteroconid and the protoconid-metaconid complexes is present in 50% of specimens ( Fig. 3I, L, P ). There is a longitudinal spur (not reaching the protoconid-metaconid intersection) in 22 out of 34 individuals ( Fig. 3I, P ). As wear advances, the longitudinal spur is usually more pronounced (SOM 2: fig. S2A). The labial cingulum is moderately developed. The large, subtriangular posterior accessory cuspid is connected to the labial face of the hypoconid by a low crest in all but two specimens (BA1-2001- R7 /47, BA1-2001- R7 /51; SOM 2: fig. S2D). There is occasionally another spur in contact with the posterior face of the hypoconid ( Fig. 3P ). There are up to three other accessory labial cuspids (see SOM 2: fig. S2I). The medium-sized posterior cingulum can be oval ( Fig. 3L ) or compressed ( Fig. 3P ). It is transversally elongated and displaced lingually. Two well-developed roots (anterior and posterior) are present .

The m2 (n = 44) displays a rather square occlusal outline, somewhat wider anteriorly than posteriorly. The moderate-sized labial anteroconid can be round or oval, and is connected basally to the weak or moderate labial cingulum. There is a small posterior accessory cuspid in 23 out of 41 specimens preserving this part ( Fig. 3K, N ). It can be oval (SOM 2: fig. S2 R, T), round ( Fig. 3N ) or subtriangular ( Fig. 3K ; SOM 2: fig. S2O) and is connected to the hypoconid in most cases. A longitudinal spur not reaching the protoconid-metaconid intersection is discernible in 49% of specimens ( Fig. 3K ); it is more pronounced as wear advances. The variable posterior cingulum is displaced lingually. It can be small or large, and oval ( Fig. 3M, N ) or compressed ( Fig. 3K ; SOM 2: fig. S2O). There are two roots (anterior and posterior) .

The m3 (n = 27) has a subtriangular occlusal outline. The labial anteroconid is absent (except for BA1-2001- R8 /11, in which it is very low and reduced; SOM 2: fig. S2AE). The posterior complex (hypoconid-entoconid pair) is separated from the protoconid-metaconid pair. The labial cingulum is weak or absent. A much reduced posterior accessory cuspid attached to the labial side of the posterior complex (hypoconid) is present in eight out of 27 specimens (BA1-2001- R8 /4, BA1-2001- R8 /10, BA1-2001- R8 /11, BA1-2001- R8 /12, BA1- 2018- R1 /20, IPS89326, IPS89327, IPS89328; see Fig. 3O ; SOM 2: fig. S2Z, AB, AH). Two roots (anterior and posterior) are present .

Stratigraphic and geographic range.—Early Pliocene(MN14) of the Iberian Peninsula: Baza-1, Gorafe-1, Gorafe-A, Gorafe-4 (Guadix-Baza Basin); Purcal-13, Calicasas-5A ( Granada Basin); Alcoy-2C, Alcoy-2D, Alcoi Barranc Sud- 2, Alcoi Barranc Sud-3, Alcoi Barranc Sud-3A, Alcoi Cristian-0, Alcoi Cristian-0B (Alcoy Basin); Sifón-P (Fortuna Basin); La Bullana-2B, La Bullana-3 (Cabriel Basin); Celadas-1, Celadas-9, La Gloria-4 (Teruel Basin).

Figures

Fig.3. Upper and lower dentition of the murid rodent Paraethomys baeticus sp.nov.from Baza-1, early Pliocene,Guadix-Baza Basin, Spain, in occlusal view. A. BA1-2001-R7/2, left M1 (holotype). B. BA1-2001-R7/5, right M1. C. BA1-2001-R7/16, right M1. D. BA1-2001-R7/22, right M2. E. BA1-2001-R7/24, right M2. F. BA1-2001-R7/25, right M2. G. BA1-2001-R8/20, right M3. H. BA1-2001-R8/17, left M3. I. BA1-2001-R7/32, right m1. J. BA1-2001-R8/12, left m3. K. BA1-2001-R7/62, right m2. L. BA1-2001-R7/43, left m1. M. BA1-2001-R7/73, right m2. N. BA1-2001-R7/78, right m2. O. BA1-2001-R8/3, right m3. P. BA1-2001-R7/48, right m1.

Fig.4. Ranges of size variation (in mm) in the upper (M1–M3) and lower (m1–m3) teeth of Paraethomys baeticus sp. nov. from Baza-1 (type locality; this paper), Paraethomys jaegeri from Gorafe-2 (type locality; Montenat and De Bruijn 1976), Paraethomys abaigari from Villalba Alta Río (type locality) and La Judería (Adrover et al. 1988), Paraethomys meini from Sète (type locality; Michaux 1969; Adrover 1986) and Sifón-61 (Piñero and Agustí 2019), Paraethomys belmezensis from Bélmez-1 (type locality; Castillo Ruiz 1992), and Paraethomys balearicus from Na Burguesa-1 (type locality; Torres- Roig et al. 2019). Mean sizes are marked by symbols inside the boxes.