A Pliocene-Pleistocene continental biota from Venezuela

Abstract

The Pliocene-Pleistocene transition in the Neotropics is poorly understood despite the major climatic changes that occurred at the onset of the Quaternary. The San Gregorio Formation, the younger unit of the Urumaco Sequence, preserves a fauna that documents this critical transition. We report stingrays, freshwater bony fishes, amphibians, crocodiles, lizards, snakes, aquatic and terrestrial turtles, and mammals. A total of 49 taxa are reported from the Vergel Member (late Pliocene) and nine taxa from the Cocuiza Member (Early Pleistocene), with 28 and 18 taxa reported for the first time in the Urumaco sequence and Venezuela, respectively. Our findings include the first fossil record of the freshwater fishes Megaleporinus, Schizodon, Amblydoras, Scorpiodoras, and the pipesnake Anilius scytale, all from Pliocene strata. The late Pliocene and Early Pleistocene ages proposed here for the Vergel and Cocuiza members, respectively, are supported by their stratigraphic position, palynology, nannoplankton, and ⁸⁶Sr/⁸⁸Sr dating. Mammals from the Vergel Member are associated with the first major pulse of the Great American Biotic Interchange. In contrast to the dry conditions prevailing today, the San Gregorio Formation documents mixed open grassland/forest areas surrounding permanent freshwater systems, following the isolation of the northern South American basin from western Amazonia. These findings support the hypothesis that range contraction of many taxa to their current distribution in northern South America occurred rapidly during at least the last 1.5 million years.

Keywords: Amblydoras; Anilius; Camelidae; Chapalmalania; Megaleporinus; Neogene; Neotropics; Northern South America; Paleodiversity; Urumaco sequence.

Fig. 1

Geographical and geological location. A Location map of the fossiliferous localities of the San Gregorio Formation. Stratigraphic section polygonal: Northward Chiguaje Hill “NCH” (see Additional file 1) and San Gregorio Río Seco “SGRS” (see Additional file 2). B Generalized geological map near the town of Urumaco showing the outcropping geological units in the area (modified after Quiroz and Jaramillo 2010). Fm. Formation, Mb. Member

Fig. 2

Fossiliferous localities of the San Gregorio Formation outcrops. A–F Norte Casa Chiguaje locality. C Close-up of the conglomeratic-fossiliferous layer. D, E Tooth (D) and humerus (E AMU-CURS-62) of mammals in situ. G, H San Gregorio Oeste del Pueblo locality. H Example of the conglomeratic layers were disarticulated continental vertebrates remains were found. Pictures from authors JDCB (A–D, G, H) and EAC (F)

Fig. 3

Stratigraphic context of the San Gregorio Formation. A Generalized section of Northward Chiguaje Hill polygonal (NCH) (see Fig. 1); a section with more detail of the NCH is presented in Additional file 1. B Norte Casa Chiguaje locality section. C San Gregorio Oeste del Pueblo locality section. The “8C_A-C” and “10C_E-F” referred in the NCH section correspond molluscan shell samples used for ⁸⁷Sr/⁸⁶Sr analyses (see Additional file 5). Fm. Formation, Mb. Member, R.S Río Seco Member

Fig. 4

Stingrays from the Vergel Member. A1–J Potamotrygon sp. (teeth A1–B3 AMU-CURS-868; C1–D3 AMU-CURS-869; E1–F3 AMU-CURS-870; G1–H3 AMU-CURS-871; and caudal spines I, J AMU-CURS-865). K1–K3 Myliobatiformes indet. Views: labial (A1, B1, C1, D1, E1, F1, G1, H1), lingual (B3, D2, H2), occlusal (A2, C2, E2, F3, G2), lateral (A3, C3, D3, E3, G3, H3), basal (B2, F2), ventral (I, J), and indet. (K1–K3)

Fig. 5

Characiformes (Anostomidae) from the Vergel Member. A1–B3 Premaxillary symphyseal teeth of cf. Megaleporinus sp. (AMU-CURS-851). C1, C2 Recent premaxillary symphyseal tooth of Megaleporinus muyscorum (PIMUZ A/I 4856). D1–O Schizodon cf. S. corti teeth (D1–G, J–L AMU-CURS-849, and H, I, M–O AMU-CURS-849), of both premaxillary (D1–I) and dentary position (J–O). P–U Recent teeth of Schizodon corti (PIMUZ A/I 4869) [premaxillary (P–R) and dentary teeth (S–U), symphyseal teeth (P and S)]. Views: labial (A3, B3, D2, E2, K2), lingual (A1, B1, C1, D1, E1, F-K1, L1, M-U), and lateral (A2, B2, C2, L2)

Fig. 6

Characiformes (Erythrinidae and Serrasalmidae) from the Vergel Member. A–F Hoplias sp. teeth of indeterminate position (A, B AMU-CURS-860 and C–F AMU-CURS-824). G1–I Recent teeth of Hoplias malabaricus (PIMUZ A/I 4875). J1–N2 Mylossoma sp. symphyseal dentary teeth (AMU-CURS-1216). O1–P2 Recent symphyseal dentary teeth of Mylossoma albiscopum (PIMUZ A/I 4860). Q Serrasalmidae indet. (? “pacu clade”) dentary tooth (AMU-CURS-859). Views: labial (A, D, I, J1, K1, L1, M1, N1, O1, P1), lingual (B, C, G1), occlusal (J2, K2, L2, M2, N2, O2, P2), and lateral (E, F, G2, H, Q)

Fig. 7

Characiformes (Serrasalmidae) and Cichliformes from the Vergel Member. A1–H Serrasalmidae indet. (? “pacu clade”). A1–D2 Molariform-like teeth from the outer row and E1–H from the inner row of indeterminate (dentary/premaxilla) position (A1, A2 AMU-CURS-859 and B1–H AMU-CURS-858). I1–M2 Dorsal (J1–J3, M1, M2), anal (K1, K2) and indeterminate position (I1, I2, L1, L2) fin spines of Cichlidae indet. (I1, I2, L1–M2 AMU-CURS-1224 and J1–K2 AMU-CURS-1223). Views: labial (A1, D1), lingual (C2), occlusal (A2, B1, C1, E1, F1), lateral (B2, C3, D2, E2, F2, G–I1, J3, K2, M2), anterior (J1, K1, L1, M1), and posterior (I2, J2, L2)

Fig. 8

Siluriformes (Ariidae, Callichthyidae, and Doradidae) from the Vergel Member. A1–A3 Dorsal spine of cf. Sciades sp. (AMU-CURS-1058). B1, B2 Recent dorsal spine of Sciades proops (PIMUZ A/I 4874). C1–E Pectoral-fin spines and F–G2 bony plate fragments of Callichthyidae indet. (C1, C2 left spine, AMU-CURS-1167a; D1–E AMU-CURS-1168 and F–G2 AMU-CURS-1169). H1–H3 Partial left cleithrum cf. Amblydoras sp. (AMU-CURS-1225). I1, I2 Recent left cleithrum of Amblydoras affinis (CAS 66236). J1–J3 Partial right cleithrum of cf. Scorpiodoras sp. (AMU-CURS-1226). K1, K2 Recent left cleithrum of Scorpiodoras heckelii (MHNLS-17959). Views: anterior (A1, B1, C2, D2), dorsal (C1, I2), dorsolateral (H1, J2), lateral (A2, B2, F–G1, H3, J3, K1, K2), mesial (J1), posterior (A3), ventral (H2), and indet. (D1, E, G2)

Fig. 9

Siluriformes (Doradidae) from the Vergel Member. A1–J Doradidae indet. A1, A2 Parieto-supraoccipital (AMU-CURS-1227). B Partial parieto-supraoccipital (AMU-CURS-1170). C Partial left cleithrum (AMU-CURS-1175). D1–J Pectoral-fin spines (D1–H3 AMU-CURS-1234 and I, J AMU-CURS-1233), position: right (D1–H3) and indet. (I, J). K1–L3 Right pectoral-fin spines of extant Anadoras wedellii (K1–K3 AUM-45441) and Scorpiodoras heckelii (L1–L3 MHNLS-17959). Views: anterior (D2, H2, L2), dorsal (A1, B, C, D1, E1, F1, G1, H1, K1, L1), posterior (D3, E2, F2, G2, H3, K3, L3), ventral (A2, E3, K2), and indet. (I, J). atp anterior process, artg articular grove, dpr dorsal process, vpr ventral process

Fig. 10

Siluriformes (Doradidae, Heptapteridae, and Loricariidae) from the Vergel Member. A1–D2, G–I2 Dorsal-fin spines (A1–D2 AMU-CURS-1180) and mid-lateral scutes (G, H AMU-CURS-864a-b and I1, I2 AMU-CURS-1232a) of Doradidae indet. E1–F3 Dorsal spines of extant Anadoras wedellii (E1, E2 AUM-45441) and Scorpiodoras heckelii (F1–F3 MHNLS-17959). J Pectoral spine of cf. Pimelodella sp. (AMU-CURS-1183). K1–P Pectoral spine fragments (K1–l2 AMU-CURS-1173 and M–N2 AMU-CURS-817), and odontodes (O, P AMU-CURS-876) of Hypostominae indet. Q, R Body plates of Loricariidae indet. (AMU-CURS-1230). Views: anterior (A1, B1, C1, D1, E1, F1, K2, L1, N2), lateral (A2, B2, C2, D2, E2, F2, I2, O–P) posterior (A3, F3), and indet. (G–I1, J, K1, L2, M, N1, Q–R). atp anterior process, atf articular foramen, mp medial process

Fig. 11

Siluriformes (Pimelodidae and indet.) from the Vergel Member. A1–B3 Left pectoral spines of cf. Platysilurus sp. (AMU-CURS-1172). C1–C3 Left pectoral spine of extant Platysilurus malarmo (ANSP 187009). D1–E3 Left (D1–D3) and right (E1–E3) pectoral spines of Pimelodidae indet. (AMU-CURS-1228). F–M Partial left cleithrum (F AMU-CURS-1237), skull fragments (G, H AMU-CURS-1175), precaudal vertebra (I1, I2 AMU-CURS-1174), first dorsal spine (J AMU-CURS-1181), right pectoral spines (K AMU-CURS-867), and pectoral spine fragments (L AMU-CURS-867 and M AMU-CURS-1229) of Siluriformes indet. Views: anterior (A3, B3, C3, D3, E2, I1, J), lateral (I2), posterior (A2, B2, C2, D2, E3), dorsal (A1, B1, C1, D1, E1, F), anterodorsal (K), and indet. (G, H, L, M). atp anterior process, artg articular grove, dpr dorsal process, vpr ventral process

Fig. 12

Synbranchus sp. from the Vergel Member. A1–C3 Dentaries (right: A1–A3, C1–C3, and left: B1–B3; AMU-CURS-1146-a-c) and branchial bones (D1, D2 AMU-CURS-1146-d). E1–F2 Right (E1, E2) and left (F1, F2) dentaries of extant Synbranchus marmoratus (PIMUZ A/I 4873). G1–J Isolated vertebrae of Synbranchus sp. (AMU-CURS-1171). Views: anterior (G1, H1, I1), left lateral (B1), right lateral (A1, C1, E2), lateral (D1, J), medial (A3, B3, C3, F2), occlusal (A2, B2, C2, E1, F1), and ventral (D2, G2, H2, I2)

Fig. 13

Actinopterygii indet from the Vergel Member. A–D Pharyngeal (C, D AMU-CURS-1145) and other teeth of indeterminate position (A, B AMU-CURS-1178). E, F Ceratobranchial bones (AMU-CURS-1238). G–M Isolated vertebrae (AMU-CURS-1177). N–Q Isolated scales (AMU-CURS-863). Views: anterior (G, H1, I1, J1, K1, L1, M), Dorsal (J2, K2), lateral (A–D, H2, I2), ventral (L2), and indet. (N–Q)

Fig. 14

Anura from the Vergel Member. A1, A2 Incomplete fused sacral vertebra of cf. Pipa sp. (AMU-CURS-722). B1, B2 Sacral vertebra of recent Pipa parva (PIMUZ A/II 118). C1–L Anura indet. C1–F2 Maxilla fragments (C1–C3 AMU-CURS-1177, D1, D2 AMU-CURS-1149, E AMU-CURS-1166 and F1, F2 AMU-CURS-1165). G Distal fragment of a left ilium (AMU-CURS-1150). H Distal portion of left humerus (AMU-CURS-1152). I Spinous process of and incomplete trunk vertebra (AMU-CURS-1153). J Distal fragment of a right radioulna (AMU-CURS-1151). K, L Indeterminate limb bone fragments (AMU-CURS-807). Views: dorsal (A1, B1, I, ?J), left lateral (G), right lateral (F1), lateral (C1, D1), lateroventral (C2), ventral (A2, B2, C3, D2, E, F2, H), and indet. (K, L). ssdr sacral sagittal dorsal ridge, sf spinal foramen

Fig. 15

Testudines (Testudinidae, Chelidae, and Podocnemididae) from the Vergel (A1–D, G1–I2, K1–L2) and Cocuiza (E1–F, J) members. A1–A3 Incomplete right femur of Chelonoidis sp. (AMU-CURS-584). B1, B2 Anterolateral portion of a left xiphiplastron of Chelus sp. (AMU-CURS-839). C1–K2 Podocnemididae indet. C1–C5 Cervical vertebra (AMU-CURS-571). D Left ilium (AMU-CURS-675). E1, E2 Left ischium (AMU-CURS-1305). F Peripheral bone from the posterior margin of the carapace (AMU-CURS-1307). G Peripheral bone from the bridge region of the shell (AMU-CURS-838). H1, H2 Partial right hypoplastron (AMU-CURS-580). I1, I2 Lateral portion of a costal bone, potentially left costal 5 (AMU-CURS-547). J Costal bone potentially the right costal 6 (AMU-CURS-1306). K1, K2 Posterior tip of a right xiphiplastron (AMU-CURS-79). L1, L2 Peripheral bone from the carapace-plastron bridge region (AMU-CURS-579). Views: anterior (A2), dorsal (C3, E1, F), cross‐sectional (G2, L2), internal (B1, H2, I2, K1), external (B2, H1, I1, J, K2, L1), left lateral (C1), right lateral (A3, C2), lateral (D, G1), posterior (A1, C5), and ventral (C4, E2)

Fig. 16

Testudines indet. and (non-snake) Squamata from the Vergel Member. A–E Testudines indet. A Fragment of a right premaxilla (AMU-CURS-1154). B1, B2 Distal section of a left fibula (AMU-CURS-1160). C1, C2 Plastron fragment with a bite mark (AMU-CURS-862). D, E Shell fragments (D AMU-CURS-842 and E AMU-CURS-842). F1–F3 Fragmentary right dentary of Tupinambis s.l. (AMU-CURS-721). G–K (Non-snake) Squamata indet. G Anterior section of a left maxilla (AMU-CURS-1148). H1, H2 Right jaw fragment preserving three complete teeth (AMU-CURS-1164). I Premaxilla fragment with an incomplete tooth (AMU-CURS-1163). J, K Two maxilla fragments (J AMU-CURS-725 and K AMU-CURS-797). Views: anterior (B2), external (C1–E), left lateral (G), right lateral (A, F2), mesial (F3, H2, I–K), occlusal (F1, H1), and posterior (B1)

Fig. 17

Serpentes (Aniliidae and Boidae) from the Vergel Member. A1–A5 Trunk vertebra of Anilius scytale (AMU-CURS-1159). B1–B5 Trunk vertebra of Corallus sp. (AMU-CURS-1157). C1–C5 Trunk vertebra of Eunectes sp. (AMU-CURS-1304). Views: anterior (A3, B3, C3), dorsal (A1, B1, C1), right lateral (A5, B5, C5), posterior (A4, B4, C4), and ventral (A2, B2, C2)

Fig. 18

Serpentes (Boidae and Colubroides) from the Vergel Member. A1–B3 Trunk vertebra (A1–A5 AMU-CURS-1147) and specimen of indeterminate position (B1–B3 AMU-CURS-804) of Boidae indet. C1–C5 Trunk vertebra of ?Boidae or ?Aniliidae indet. (AMU-CURS-1158). D1–D5 Trunk vertebra of Colubroides indet. (AMU-CURS-1161). E1–G Trunk vertebra (E1–E4 AMU-CURS-803), fragmented prezygapophysis (F AMU-CURS-724), and a trunk vertebra (G AMU-CURS-805) of Serpentes indet. Views: anterior (A3, B3, C3, D5, E3), dorsal (A1, B1, C1, D1, E1), left lateral (D3), right lateral (A5, C5, D4, E4), posterior (A4, C4), and ventral (A2, B2, C2, D2, E2, G)

Fig. 19

Crocodylia (Caimaninae) from the Vergel (B–F, H–L) and Cocuiza (A1–A3, G1, G2) members. A1–A3 Right maxilla fragment of Caiman aff. C. yacare (AMU-CURS-1328). B–L Caimaninae indet. B–J Osteoderms (B–D AMU-CURS-553, E–F AMU-CURS-711, G1, G2 AMU-CURS-1315 and H–J AMU-CURS-1060a), skull fragment (L), and one cervical rib (K) (AMU-CURS-1060b). Views: cross sectional (G2), dorsal (A1, L), external (B–G1, H–J), lateral (K), right lateral (A3), and ventral (A2)

Fig. 20

Crocodylia indet. from the Vergel (A1, B2, D, F–N, P–R) and Cocuiza (C, E, O1, O2, S–T2) members. A1–I2 Teeth (A1, A2, F–H AMU-CURS-861, B1, B2 AMU-CURS-167, C AMU-CURS-1352, D AMU-CURS-574, E AMU-CURS-1322 and I AMU-CURS-1095). J1–T2 Osteoderms (J1, J2 AMU-CURS-033, K1, K2 AMU-CURS-030, L1, L2 AMU-CURS-593, M, N, Q AMU-CURS-594, O1, O2 AMU-CURS-1311, P AMU-CURS-1184, R AMU-CURS-830, S AMU-CURS-1313, and T1, T2-1312). Views: cross sectional (L1, O2), external (J1, K1, M–O1, P–T1), internal (J2, K2), labial (A1, C, E–G), lateral (A2, B2, I2, L2, T2), and lingual (B1, D, H–I1)

Fig. 21

Crocodylia indet. from the Vergel (A, F, H–P) and Cocuiza (B, C, D1–E, G) members. A–C Osteoderms (A AMU-CURS-1029, B AMU-CURS-1314, and C AMU-CURS-1316). D1, D2 Portion of a left dentary (AMU-CURS-1320). E Portion of either skull or lower jaw (AMU-CURS-1321). F Fragment from the skull roof (AMU-CURS-1200). G Posterior part of a surangular (AMU-CURS-1309). H Humeral shaft (AMU-CURS-743). I1–N Vertebrae (I1, I2 AMU-CURS-21, J1, J2 AMU-CURS-826, K1, K2 AMU-CURS-1030, L1, L2 AMU-CURS-578a and M1–N AMU-CURS-1062). O Isolated prezygapophysis (AMU-CURS-1236). P Rib fragment (AMU-CURS-578b). Views: anterior (M1), dorsal (D1, F, K2, L2, O), external (A–C), left lateral (D2, I1, J1, G), posterior (M2–N), ventral (H, I2, J2–K1, L1), and indet. (E, P)

Fig. 22

Metatheria (Didelphidae) and Xenarthra (Megatheriidae) from the Vergel (A1–B3) and Cocuiza (C1–C3) members. A1–A3 Right humerus (AMU-CURS-1140) of cf. Didelphis sp. B1–C3 Skull (B1–B3 AMU-CURS-184) and left molariform Mf3 (C1–C3 AMU-CURS-1303) cf. †Proeremotherium sp. Views: anterior (A2, C2), dorsal (B2), labial (C3), mesial (A3), posterior (A1), left lateral (B1), occlusal (C1), and ventral (B3). cf coronoid fossa, ef entepicondylar foramen, lc lateral condyle, mc medial condyle, me medial epicondyle, Mf upper molariform, oc occipital condyle, of olecranon fossae, rzp right zygomatic process

Fig. 23

Xenarthra (Mylodontidae, Glyptodontidae, and Pampatheriidae) from the Vergel (A1–E2, H1, H2) and Cocuiza (F1–G2, I1–I3) members. A1–A3 Right humerus (AMU-CURS-62) of Mylodontidae indet. B, C Carapace osteoderms (AMU-CURS-1242) of dorsal or postero-dorsal (B) and indeterminate position (C) of aff. Boreostemma sp. D1–G2 Movable osteoderms (D1, D2 AMU-CURS-1063, and E1, E2 AMU-CURS-1119), and fixed osteoderms of pelvic buckler (F1, F2 AMU-CURS-1295, and G1, G2 AMU-CURS-1294) of aff. Holmesina floridanus. H1, H2 Fixed osteoderm of pelvic buckler (AMU-CURS-736) of aff. Plaina sp. I1–I3 Incomplete caudal vertebra (AMU-CURS-1356) of Xenarthra indet. Views: anterior (A1, I2), cross sectional (D2, E2, F2, G2, H2), external (B–D1, E1, F1, G1, H1), left lateral (I1), medial (A3), and posterior (A2, I3)

Fig. 24

Litopterna (Proterotheriidae) and Notoungulata (Toxodontidae) from the Vergel Member. A1–B2 Metacarpal (A1–A3 AMU-CURS-742) and distal epiphysis of a metacarpal (B1, B2 AMU-CURS-1189) of indeterminate position assigned to Proterotheriidae indet. C1–K2 Teeth of Falcontoxodon sp. C1–D3 Upper incisors: I2 (C1–C3 AMU-CURS-825) and I1 (D1–D3 AMU-CURS-1335). E1–E3 Right upper premolar P4 (AMU-CURS-1331). F1, F2 Right upper molar M1 or M2 (AMU-CURS-1346). G1–H3 Lower incisors i1 or i2 (G1–G3 AMU-CURS-828 and H1–H3 AMU-CURS-888). I1–K2 Lower premolars left p4 (I1, I2 AMU-CURS-831), right p4 (J1, J2 AMU-CURS-1337), and left p4 (K1, K2 AMU-CURS-1338). Views: anterior (A1), distal (B1, E3), disto-medial (B2), medial (A2), posterior (A3), occlusal (C3, D3, E2, F2, H2, I1, J1, K1), labial (E1, F1, G2, H1, I2, J2, K2), lingual (D1, G1), mesiolingual (C2), and mesial (C1, D2, G3, H3)

Fig. 25

Notoungulata (Toxodontidae) from the Vergel (A1–E3) and Cocuiza (F1–H2) members. A1–E3 Falcontoxodon sp. A1–B3 Right lower molars, m1 or m2 (A1–A3 AMU-CURS-1345 and B1–B3 AMU-CURS-1348). C1–D2 Astragali. C1, C2 Left astragalus (AMU-CURS-1202). D1, D2 Right astragalus (AMU-CURS-1330). E1–E3 Metatarsal IV (AMU-CURS-1118). F1–H2 Toxodontinae indet. F1, F2 Right partial mandible (AMU-CURS-1351). G Upper incisor (AMU-CURS-1326). H1, H2 Upper left molar (AMU-CURS-1325). Views: anterior (E1), lateral (E3, F2), distal (A3, B3), dorsal (C1, D1, E2), plantar (C2, D2), labial (A2), lingual (B2, G, H1), and occlusal (A1, B1, F1, H2)

Fig. 26

Notoungulata (Typotheria) from the Vergel Member. A1–A5 Left m3 (AMU-CURS-818) of Interatheriidae indet. B1–B3 Jaw with fused symphysis (AMU-CURS-1190) of Typotheria inc. sed. Views: distal (A3), dorsal (B1), labial (A2), lingual (A4), mesial (A5), occlusal (A1), right lateral (B3), and ventral (B2). abb.dcd abbreviated distolingual cingulid, c canine, ecfd ectoflexid, entd entoconulid, hyfd hypoflexid, hypcd hypoconulid, i incisor, mf menthal foramen, metd metaconid, pcd paraconid, pfd paralophid, ptcd protoconid, p premolar, mscd mesiolingual cingulid

Fig. 27

Rodentia (Caviomorpha) from the Vergel Member. A1–B2 Right dentary (A1, A2 AMU-CURS-744) and left molar M1 or M2 (B1, B2 AMU-CURS-1222) of ?Hydrochoeropsis wayuu. C1–E2 Fragmented cheek teeth (C1, C2 AMU-CURS-1186, ?pr. IIa’’ and pr. IIb of a right m3; D1, D2 AMU-CURS-1188, ?pr. 1 of a left M1 or M2, and E1, E2 AMU-CURS-1187, ?pr. IIa and pr. IIb’ of left m1) of Hydrochoerinae indet. F1, F2 Left dp4 (AMU-CURS-1220) of Neoepiblemidae indet. G1–G3 Left M1 or M2 (AMU-CURS-1221) of Marisela gregoriana. H–J2 ?Caviomorpha indet. H, I Incisors of indeterminate position (H AMU-CURS-1155 and I AMU-CURS-1206). J1, J2 Tooth fragment (AMU-CURS-1235). Views: medial (A2), distal (C2, D2, E2), labial (G2), lingual (B2, F2, G3), mesial or distal (H, I, J2), and occlusal (A1, B1, C1, D1, E1, F1, G1, J1). cp condylar process, ia incisor alveolus, mf mandibular foramen, m lower molar, and p lower premolar

Fig. 28

Artiodactyla (Camelidae) and Carnivora (Procyonidae) from the Cocuiza Member. A1–A5 Proximal portion of a right femur (AMU-CURS-1329) of Camelidae indet. B1–B4 Partial left hemimandible (AMU-CURS-1327) of Chapalmalania sp. Views: anterior (A1), lateral (A3, B1), proximal (A5), medial (A6, B2), occlusal (B3, B4), posterior (A2). fh femoral head, fv fovea, gt greater trochanter, itc intertrochanteric crest, tf trochanteric fossa

Fig. 29

Indeterminate mammalian remains and coprolites from the Norte Casa Chiguaje (A1–A4, C1–G2) and San Gregorio Oeste del Pueblo (B1–B3, H1, H2) localities. A1–A4 3rd right metatarsal (AMU-CURS-1096). B1–B3 Incomplete ?caudal vertebra (AMU-CURS-1293). C1, C2 Distal portion of a tibia (AMU-CURS-1198). D1, D2 ?right fibula (AMU-CURS-1197). E1–E3 podial phalange (AMU-CURS-1124). F1–G2 Ungual phalanges (AMU-CURS-1127). H1, H2 Presumed crocodylian coprolite (AMU-CURS-1318). Views: anterior (A3, B1, C1, D1), cross sectional (H2), dorsal (B2, E1, F1, G1), distal (C2), lateral (A1, E2, G2, H1), medial (A4, F2), right lateral (D2), proximal (A2, E3), and ventral (B3)

Fig. 30

New chronostratigraphy for the San Gregorio Formation. The age (Ma, million years ago) is derived from multiple palynological, nannoplankton, and foraminifera and ⁸⁷Sr/⁸⁶Sr analyses (see Additional files 3, 4, 5)

Fig. 31

Freshwater and terrestrial vertebrate diversity of the San Gregorio Formation by localities. Information based on Table 1

Fig. 32

Sample size-based sampling curves for mammals and fishes recorded in Norte Casa Chiguaje. The plots show the rarefaction (solid lines), and extrapolation (dotted lines) sampling and the 95% confidence intervals (shaded areas) for the generic richness of mammals and fishes

Fig. 33

Internal seed casts from the Norte Casa Chiguaje locality (Vergel Member). A1, A2 Morphotype 1 (AMU-PB-02), Poaceae aff. Chloroideae. B1–C2 Morphotype 2 (AMU-PB-03), Cucurbitaceae. D1–E2 Morphotype 3 (AMU-PB-04), of indeterminate affinities. F1–H Morphotype 4 (AMU-PB-05), Amaranthaceae. I–K Morphotype 5 (AMU-PB-06), aff. Cleomaceae. L Morphotype 6 (AMU-PB-07), Asteraceae. M1–O Morphotype 7 (AMU-PB-09), aff. Vitaceae. P1–P2 Morphotype 8 (AMU-PB-10) of indeterminate affinities

Fig. 34

Freshwater molluscs and crustaceans from the Vergel Member. A–D Internal molds of indeterminate bivalves (AMU-PI-81). E–H Internal molds of gastropods (AMU-PI-82) presumably related to Planorbidae. J, K Internal molds of indeterminate gastropods (AMU-PI-83). L–O2 Right chelae (L, M) and moveable fingers (dactyl: N1–O2) of indeterminate freshwater crabs Trichodactylidae (AMU-PI-15)

Fig. 35

(Top) Life reconstruction of the San Gregorio Formation faunal assemblage, Falcón Basin, Venezuela. Artist: Jaime Chirinos. (Bottom) Key of the reconstruction. (1) cf. Didelphis sp. (2) cf. †Proeremotherium sp. (3) aff. †Holmesina floridanus. (4) †Pliodasypus vergelianus. (5) Podocnemididae indet. (6) Anilius scytale. (7) Chelus sp. (8) †Crocodylus falconensis. (9) †Cyonasua sp. (10) †Interatheriidae indet. (11) Podocnemididae indet. (12) †Falcontoxodon sp. (13) †?Hydrochoeropsis wayuu. (14) aff. †Boreostemma sp. (15) Tupinambis s.l. (16) †Marisela gregoriana. (17) Corallus sp. (18) Chelonoidis sp. (19) Lizard. (20) Mylossoma sp. (21) Potamotrygon sp. (22) Hoplias sp. (23) Schizodon cf. S. corti. (24) cf. Amblydoras sp. (25) Cichlidae indet. (26) Caimaninae indet. (27) cf. Megaleporinus sp. (28) cf. Sciades sp. (29) Callichthyidae indet. (30) Eunectes sp. (31) cf. Pipa sp. (32) Synbranchus sp. (33) Suckermouth catfish (Hypostominae)