Orangel Aguilera

Neogene vertebrates from Urumaco, Falcón State, Venezuela: Diversity and significance

Synopsis The first palaeontological discoveries in Urumaco were made more than half a century ago. Several research groups have worked in the region, but new vertebrate fossils are still being found in this area of northwestern Venezuela. The most conspicuous elements of the fauna are reptiles, because of their size and abundance, although fishes are by far the most diverse group. Among South American Neogene assemblages the whole fauna is most similar to those of Acre in Brazil and Entre Rios in Argentina. The crocodile fauna includes at least 12 species representing diverse ecomorphological types; most of them lived sympatrically, a unique case in worldwide crocodylomorph assemblages. At least four turtle species provide unique palaeobiogeographical or palaeobiological information. Several freshwater species, including Serrasalminae fish, thorny catfishes, silver croaker, redtail catfishes, matamata turtle, river dolphin and probable sirenians, are consistent with the hypothesis that a tributary and/or delta of the Orinoco existed in this area of north‐western Venezuela during late Miocene times.

AN EXCEPTIONAL COASTAL UPWELLING FISH ASSEMBLAGE IN THE CARIBBEAN NEOGENE

Abstract We report the discovery of an extremely rich, previously undescribed Caribbean late Miocene to early Pliocene ichthyofauna represented by one hundred forty species of elasmobranchs and teleosteans from the Cubagua Formation, northeastern Venezuela. The fauna exhibits significant ecological differences compared with common neritic Caribbean Neogene assemblages. The bathymetric distributions of taxa, based on living counterparts, ranges from 0 to 100 m depth. The exceptional co-occurrence of deep water (epipelagic, mesopelagic and benthopelagic), and shallow water (neritic) taxa is best interpreted as the consequence of ocean upwelling in the proximity to the deep-water Cariaco Trench. Patterns of predator and prey are established and corroborate upwelling. Special remarks are made regarding previously unknown late Miocene to early Pliocene Caribbean ichthyofaunas, the absence or rarity of reported fossil taxa in the Recent Caribbean fauna, and a paleo- upwelling indicator (Lampadena jacksoni new species).

A new giant Purussaurus (Crocodyliformes, Alligatoridae) from the Upper Miocene Urumaco Formation, Venezuela

Synopsis Fossil Crocodylia are taxonomically diverse in South America, particularly in the upper Miocene Urumaco Formation (Venezuela). Among them is the giant alligatoroid Purussaurus, previously known from the upper Miocene Solimões Formation in Brasil (P. brasiliensis) and the middle Miocene of La Venta in Colombia (P. neivensis). New specimens of Crocodylia from the Urumaco Formation are described and a new species, Purussaurus mirandai, erected. This is characterised by a large, elongate and extremely flat skull, a very large narial opening comprising almost 60% of rostral length and a large incisive foramen that extends anteriorly between the fossae for the first mandibulary teeth. Purussaurus mirandai sp. nov. was the largest predator in the swampy environments and represented the top trophic level in the Urumaco assemblage. A phylogenetic analysis of 164 characters in 68 ingroup crocodile taxa supported the association of P. neivensis and P. mirandai with five synapomorphies and confirmed the sister‐group relationship of the genus with the Nettosuchidae.

The late Miocene Phractocephalus catfish (Siluriformes: Pimelodidae) from Urumaco, Venezuela: additional specimens and reinterpretation as a distinct species

Based on additional specimens the fossil pimelodid catfish from the upper Miocene Urumaco Formation, Falcon State, Venezuela originally assigned to the extant species Phractocephalus hemioliopterus is described as a new, extinct species. x86Phractocephalus nassi n. sp. is diagnosed by the following combination of characters: 1) posterior half of frontals and anterior half of supraoccipital with elongate, coarse ridges and sulci in addition to reticulating ridges and subcircular pits; 2) very broad and ornamented mesethmoid bone; 3) lateral ethmoid margin convex and eliminating orbital notch but not projecting far anteriorly over palatine condyle; 4) anterior cranial fontanelle closed or represented by a small pit; 5) supraoccipital process rounded laterally and posterolaterally, concave posteriorly and completely concealing Weberian complex in dorsal view; 6) opercle covered with reticulating ridges and pits; 7) cleithrum coarsely ornamented along ventral edge and bulging outward lateral to spine articulation; 8) pectoral spine mostly ornamented with coarse ridges and sulci. x86Phractocephalus nassi is compared to modern P. hemioliopterus and an undescribed extinct species from the upper Miocene Solimoes Formation, Acre, Brazil. New diagnostic characters of Phractocephalus are presented that apply to the modern and fossil species, including: 1) ornamentation of skull, pectoral girdle and fin spines comprising a coarse meshwork of reticulating ridges surrounding rounded pits plus some elongate ridges and sulci; 2) supraoccipital posterior process greatly expanded laterally and posteriorly behind occipital wall; 3) lateral ethmoid and sphenotic broadly sutured behind eye; 4) anterior cranial fontanelle reduced or completely closed and posterior cranial fontanelle closed; 5) vomerine tooth plate large, roughly pentagonal to triangular in form, and with fine teeth. Today Phractocephalus ranges widely throughout the lowland Orinoco, Amazon and Essequibo basins. However, the genus does not occur west or north of the Andes or Venezuelan coastal ranges. Recognizing the Urumaco Phractocephalus as a distinct species does not alter the obvious conclusion that this catfish marks a large river connection between the Caribbean coastal region and the Orinoco system during at least part of the Neogene. Other Urumaco fossils show this same biogeographic relationship.

T HE FOSSIL RECORD OF Phoberomys pattersoni M ONES 1980 (M AMMALIA , R ODENTIA ) FROM U RUMACO (L ATE M IOCENE , V ENEZUELA ), WITH AN ANALYSIS OF ITS PHYLOGENETIC RELATIONSHIPS

Synopsis An almost complete skeleton of Phoberomys pattersoni is reported from the Urumaco Formation in northwestern Venezuela. Phoberomys attained the largest body size among known rodents and it lived during the Late Miocene and/or Early Pliocene of Argentina, Brazil and Venezuela. Phoberomys pattersoni is probably the second largest species within its genus. The lower molar enamel shows little difference in thickness between the trailing and leading edges in the first and second lophs, whereas in the third loph the trailing edge is much thinner than the leading edge. In the leading edge of the distal loph the enamel consists of two layers, each covering approximately 50% of the entire enamel thickness, one consisting of thick H unter‐Schreger bands inclined 15–20? towards the occlusal surface, the other formed by radial enamel with the prisms inclined towards the occlusal surface. The postcranial skeleton shows a mosaic of unusual features among caviomorphs (e.g. absence of a supratrochlear foramen) and shared conditions (e.g. tuber calcis of the calcaneum that is wider than deeper dorsoventrally) that evolved in parallel in different lineages. The phylogenetic position of Phoberomys is determined on the basis of a simultaneous analysis of molecular and morphological data of select rodents. Phoberomys appears as the sister group of the Recent genus Dinomys. Several derived character conditions are shared with Dinomys: presence of a site for attachment for the m. rectus femoris on the lateral side of the innominate in the shape of an elongated crest; trochlear ridges of the femur proximally convergent; medial condyle of the femur wider than the lateral one in posterior view; medial ridge of the astragalar trochlea reaches posteriorly further than the lateral one; proximal portion of the coronoid process extends further anteriorly than the medial (and distal) process (or anconeal process). More than one species of Phoberomys may be present in the Urumaco Formation.

Fossil snakes from the Neogene of Venezuela (Falcón state)

Synopsis The first fossil snakes from Venezuela are described from three different Formations: Colombophis cf. C. portai and Boinae indet. from the Middle Miocene Socorro Formation, Boinae indet. from the Late Miocene Urumaco Formation and Viperidae indet. from the Pleistocene gravels at Cucuruchu. Although the Socorro and Urumaco Formations Boinae cannot be unambiguously referred to any particular taxa, the Venezuelan record, combined with the fauna from La Venta in Colombia, demonstrate that Boinae had achieved much of its more Northern distributions by the middle‐late Miocene. The occurrence of a viperid in the Pleistocene gravels at Cucuruchu is consistent with a geologically young record of the lineage in South America.

TWO NEW OTOLITH-BASED SCIAENID SPECIES OF THE GENUS PLAGIOSCION FROM SOUTH AMERICAN NEOGENE MARINE SEDIMENTS

Abstract Two new Neogene South American croakers of the genus Plagioscion (Perciformes, Sciaenidae) from marine sediments, Plagioscion marinus and Plagioscion urumacoensis, are described. These are otoliths from the lower Miocene Castillo, Cantaure and upper Miocene Urumaco Formations of the Neogene Venezuelan basin, respectively. An additional undetermined fossil species of Plagioscion was also collected from the upper Miocene to lower Pliocene Cubagua Formation. Using the function total fish length = 13.7187 + 50.8399 * Ln otolith size, the total length of P. marinus n. sp. is inferred to be from 6.05 to 38.1 cm, and for the specimens of P. urumacoensis n. sp. it is 63.3 cm. The length distribution of the fossil species overlaps the length distribution of the living freshwater species.

GOLIATH GROUPER (PISCES: SERRANIDAE) FROM THE UPPER MIOCENE URUMACO FORMATION, VENEZUELA

T he goliath grouper (family Serranidae, subfamily Epinephelinae) inhabits tropical and subtropical waters. The Epinephelinae serranids are comprised of about 159 species in 15 genera (Heemstra and Randall, 1993) and are represented in all oceans. According to Heemstra and Randall (1993) the goliath grouper Epinephelus itajara (Lichtenstein, 1822) occurs in the eastern Atlantic Ocean from Florida to Brazil, throughout the Gulf of Mexico and in the Caribbean Sea, in the western Atlantic Ocean from Senegal to the Congo, and in the eastern Pacific Ocean from the Gulf of California to Peru. The maximum size is about 250 cm total length and they can exceed 320 kg in weight. The grouper Epinephelus lanceolatus (Bloch, 1790) occurs throughout the Indo-Pacific region, from the Red Sea to Algoa Bay, South Africa, and eastward to the Hawaiian and Pitcairn Islands, and in the western Pacific Ocean from southern Japan to Australia in the south. The maximum size is about 231 cm total length (Schultz, 1966) and 400 kg in weight (Fourmanoir and Laboute, 1976). These two species are the largest serranids in the world. Sadovy and Eklund (1999) noted that males reach a maximum age of 26 and females 37 years in a population of E. itajara .nnFossil specimens of Epinephelus Bloch, 1793 are known only from Caribbean Neogene otoliths (Nolf, 1976; Nolf and Stringer, 1992; Nolf and Aguilera, 1998; Stringer, 1998; Aguilera and Rodrigues de Aguilera, 1999, 2001) and from Atlantic Neogene skeletal remains (Purdy et al., 2001). In this paper we describe the first large and complete fossil neurocrania of Epinephelus itajara and associated bones obtained from the upper Miocene Urumaco Formation (upper member) of Venezuela. These specimens provide an example of a very long-lived tropical marine species, and the explanation for its present amphitropical American …