10 research outputs found
Middle-late Miocene palaeoenvironments, palynological data and a fossil fish Lagerstätte from the Central Kenya Rift (E. Africa).
No full textThe Miocene epoch was a time of major change in the East African Rift System (EARS) as forest habitats were transformed into grasslands and hominids appeared in the landscape. Here we provide new sedimentological and palynological data on the middle–upper Miocene Ngorora Formation (Tugen Hills, Central Kenya Rift, EARS), together with clay mineral characterizations, mammal finds and a description of the Ngorora fish Lagerstätte. Furthermore, we introduce a revised age of c. 13.3 Ma for the onset of the Ngorora Formation. The older part of the Ngorora Formation (c. 13.3–12 Ma) records low-energy settings of lakes, floodplains and palaeosols, and evidence of analcime indicates that lakes were alkaline. The palynomorph spectrum consists of tree pollen (Juniperus, Podocarpus), Euphorbiaceae pollen (Acalypha, Croton) and herbaceous pollen of Poaceae and Asteraceae, suggestive of wooded grasslands or grassy woodlands. Alkaline lakes, floodplains and palaeosols continue upsection (c. 12–9 Ma), but environmental fluctuations become more dynamic. Paucity of palynomorphs and the presence of an equid may point to progressively drier conditions. A total of about 500 articulated fish fossils were recovered from distinctive layers of almost all sections studied and represent different lineages of the Haplotilapiines (Pseudocrenilabrinae, Cichlidae). Some of the fish kills may be attributable to rapid water acidification and/or asphyxiation by episodic ash falls. Repeated instances of abrupt change in water depth in many sections are more likely to be due to synsedimentary tectonic activity of the Central Kenya Rift than to climatic variation. Overall, the preservation of the Ngorora fish Lagerstätte resulted from the interplay of tectonics, formation of alkaline lakes and explosive volcanism. As records of grasslands that pre-date late Miocene time are rare, our finding of middle Miocene (12–13 Ma) grassy savannah in the Central Kenya Rift is also relevant to models of human evolution in East Africa
Morotochoerus de Uganda (17.5 Ma) y Kenyapotamus de Kenia (13-11 Ma): implicaciones sobre el origen de los hipopotámidos
No full textThe aim of this paper is to describe and interpret suiform teeth from Moroto, Uganda, and Ngorora, Kenya, which contribute to the debate about hippo-anthracothere-whale relationships. The early stages of hippopotamid evolution are relatively poorly known on account of the paucity of their fossil record older than 7 Ma. New specimens of Morotochoerus from Uganda reveal that it is not closely related to Hippopotamidae; the superficial resemblances of the cheek teeth to those of hippos represent convergences and not homologies. Restricted samples of Palaeopotamus ternani are available from the Middle Miocene of Kenya {Maboko, ca 16 Ma; Muruyur, ca 14.5 Ma; Fort Ternan, ca 13.7 Ma} while from the base of the late Miocene, Kenyapotamus coryndonae is known from Kenya {Ngerngerwa, ca 10.5-10 Ma; Nakali, ca 10.5 Ma; Samburu Hills, ca 9.5 Ma}, Ethiopia {Ch’orora, ca 10.5 Ma} and Tunisia {Beglia Formation ca 11-10 Ma}. The recovery of specimens of Kenyapotamus from the Ngorora Formation, Kenya, aged ca 11 Ma, is of interest because it includes well preserved teeth, including an m/3 in good condition. These specimens support the hypothesis that hippopotamids descended from palaeochoerids and not from anthracotheres.El objetivo de este trabajo es describir e interpretar los dientes suiformes de Moroto, Uganda, y Ngorora, Kenia, que contribuyen al debate sobre las relaciones hipo-anthracothere-whale. Las primeras etapas de la evolución de los hipopotámidos son relativamente poco conocidas a causa de la escasez de su registro fósil en edades superiors a los 7 Ma. Nuevos ejemplares de Morotochoerus en Uganda revelan que no están estrechamente relacionados con Hippopotamidae, las semejanzas superficiales de los dientes de la mandíbula con los de los hipopótamos representan convergencias y no homologías. Algunas muestras de Palaeopotamus ternani aparecen en el Medio Mioceno de Kenia {Maboko, ca 16 Ma; Muruyur, ca 14.5 Ma; Fort Ternan, ca 13.7 Ma}, mientras que desde la base del Mioceno tardío, Kenyapotamus coryndonae aparece en Kenia {Ngerngerwa, ca 10.5-10 Ma; Nakali, ca 10.5 Ma; Samburu Hills, ca 9,5 Ma}, {Ch’orora Etiopía, ca 10.5 Ma} {y Túnez Beglia Formación ca 11-10 Ma}. La obtención de especímenes de Kenyapotamus de la Formación Ngorora, Kenya, con edad ca 11 Ma, es de interés porque incluye dientes bien conservados, incluyendo un m/3 en buenas condiciones. Estos ejemplares apoyan la hipótesis de que los hipotámidos descienden de paleoquéridos y no de antracotéridos
Quaternary diatomaceous sediments and the geological evolution of lakes, Turkana, Baringo and Bogoria Kenya Rift Valley.
No full textPhdQuaternary lacustrine sediments are described from
three contrasting areas within the Kenya Rift Valley.
Descriptions are given of the mid-Pleistocene Olorgesailie
Formation at Olorgesailie. (southern-, Kenya Rift Valley),
a series of lacustrine sediments deposited between the
mid-Miocene and present in the Baringo District (central
Kenya Rift Valley) and finally of Quaternary'(largely
Holocene) deposits at East Turkana (northern Kenya Rift
Valley). A wide range of environments are represented by
these deposits including offshore and littoral lacustrine,
deltaic and alluvial situations. Emphasis is placed on the
examination of lacustrine and lake marginal sediments.
Diatom assemblages found. in these deposits are described
for the first time. These have 'been studied using optical
and scanning electron microscopy. The. relationships
between diatom assemblages and sedimentary facies are
examined and evolutionary trends in certain diatoms are
discussed. The contemporary ecology of diatoms at East
Turkana is discussed and a review is given of diatom
ecology and lake classification in East Africa. Diatoms
are used to indicate transgression-regression. cycles
during the Holocene, and palaeoecological conditions
through the Quaternary. Mapping in conjunction with some
altimetric data is used to indicate the location, extent
and height of several Holocene lacustrine still-stands.
Geochemical and sedimentological data is presented for
the Holocene deposits at East Turkana and in the Baringo
District. Several erosional and depositional processes
operating at East Turkana are briefly discussed. A
classification of Holocene environments at East T»rksna
is presented.
The palaeogeography of the northern Kenya Rift Valley
and the development of diatom floras during the Holocene
is discussed. Data presented here and in the literature
is considered and reviewed from a palaeoclimatic viewpoint.
The development of Lakes Turkana, Baringo and Bogoria
through the Quaternary are also considered.
Conclusions are drawn as to the value of diatoms in
palaeoecology and stratigraphy
Deep structure of the Baringo Rift Basin (central Kenya) from three-dimensional magnetotelluric imaging: Implications for rift evolution
No full textThree-dimensional modeling of data from 31 vertical electrical and 24 magnetotelluric soundings collected in the Baringo-Bogoria Basin (central Kenya Rift Valley) shows a thick succession of well-defined tectonostratigraphic units beneath the Recent deposits of the Marigat-Loboi Plain. They include from top to bottom, a sedimentary basin, ∼1.5 km thick, controlled by N-S and N140° structural trends, and a thick homogeneous resistive layer related to the bottom of the basin, overlying a conductive structure, which cannot be clearly correlated with the Proterozoic basement. It is suggested that the resistive layer correlates with the mid-Miocene plateau-type flood phonolites which flowed over the early Kenya Rift during a major volcanic activity period. The conductive structure overlain by these lava flows could be a sedimentary basin developed during the initial phase of rifting, during the Oligocene-Miocene. The absence of a significant gravity low associated with this deep basin suggests a zone of dense intrusion deeper than 5–10 km, not discernible with the magnetotelluric data but required to explain the gravity anomalies. The recognition of a deeply buried sedimentary succession lying between 4 and 8 km beneath the lower Miocene volcanic series of the Baringo valley would provide new insights into the regional volcano-sedimentary stratigraphie succession and the rift development of the Kerio and Baringo Basins
Percrocuta tobieni Crusafont & Aguirre 1971
No full textPercrocuta tobieni Crusafont & Aguirre, 1971 Percrocuta tobieni Crusafont & Aguirre, 1971: 55. TYPE SPECIMEN. — KNM-BN 1469, right mandible corpus with c, p2-m1. TYPE LOCALITY. — Kabarsero, Ngorora Formation, Kenya. MATERIAL EXAMINED. — KNM-FT 3362, right dp4; KNM-FT 3364, right dP3; KNM-FT 3375a, right m1; KNM-FT 3375e, left P2; KNM-FT 3408, right dP2; KNM-FT 3610, left P3; KNM-FT 3614a, right maxilla with P1 (emerging) and dP2-dP4; KNM-FT 3614b, right maxilla fragment with P3-P 4 in crypt; KNM-FT 3614c, right M1; KNM-FT 12693, left p3; KNM-FT 12694, broken left p4; KNM-FT 12695, left mandible corpus with alveolus for dp2, complete dp3-dp4, emerging m1; KNM-FT 14140, right p3. DESCRIPTION KNM-FT 3362 (Fig. 3E, F) A long, slender deciduous carnassial in which the paraconid is longer and lower than the protoconid. The metaconid is well developed and set distal to, and well separate from, the protoconid. The talonid bears small, crestiform entoconid and hypoconid. The position of the metaconid and development of the talonid identify the specimen as Percrocutidae. Measurements. Ldp4 16.6; Wdp4 6.2. KNM-FT 3364 (Fig. 3 G-H) A dP4 that is broken anteriorly. The extent of the preparastyle is not clear, but it appears to have formed a distinct cusp. The parastyle cusp is large and triangular. It is located mesiolingual to the paracone. The protocone is reduced to a low lingual bump. The paracone is the tallest cusp and is rhomboid in occlusal view. The preparacrista is strong. The metastyle is long, straight and low. There are no distinct cingula. Measurements. LdP4 18.3+; WadP4 7.3; WbldP4 5.7; LpdP4 5.6; LmdP4 6.4. KNM-FT 3375a A trenchant carnassial with paraconid and protoconid that are subequal in length, with the latter being the taller of the two. The metaconid is absent. The talonid is very reduced and shows evidence of only a very small and weak hypoconid. The mesial root is large and the distal root is small. Measurements. Lm1 22.4; Wm1 11.3; Ltm1 18.9. KNM-FT 3375e A small, robust P2 with prominently wrinkled enamel. The mesial accessory cusp is small and low, set mesiolingually and appressed to the main cusp. The latter is pyramidal, with strong mesiolingual and distal crests. The distal accessory cusp is low but sharp and is less appressed to the main cusp than is the mesial accessory cusp. Measurements. LP2 12.0; WP2 7.8. KNM-FT 3408 A long, relatively slender dP2. The mesial accessory cusp is very low and set mesiolingual to the main cusp. In occlusal view the mesial shelf of the tooth is longer than the distal shelf. The main cusp is tall and ovoid in occlusal outline. The distal accessory cusp is more distinct than the mesial accessory cusp but set in a truncated shelf. There is a lingual root that in occlusal view forms a bulge near the base of the enamel on the lingual side. Measurements. LdP2 11.6; WdP2 6.4. KNM-FT 3610 A tall, pyramidal P3. The mesial accessory cusp is low but distinct, set mesiolingual to the main cusp and only somewhat appressed to it. The main cusp is tall and nearly round in occlusal outline. It has strongly wrinkled enamel. The distal accessory cusp is strong, somewhat trenchant and set away from the main cusp in a short shelf. Measurements. LP3 17.8; WP3 12.0. KNM-FT 3614a (Fig. 3C, D) This maxilla includes three deciduous teeth in position. The DP2 is in every respect similar to KNM-FT 3408 described above, except for being nearly unworn. An occlusal view clearly shows the slight lingual bulge of the lingual root. The DP3 is complete and shows the anteriormost cusp to be large, with transverse shear. The preparastyle is identical to that of KNM- FT 3375a. The protocone shelf is more distinct than in that tooth, but is still very low, with an almost obliterated cusp. The paracone is relatively shorter than in KNM-FT 3375a and the metastyle appears slightly less straight than in that tooth. The DP4 is large and subtriangular, with a distinct, though worn paracone bordered buccally by a cingulum. There is also a low, very worn metacone, and a large, crescentic protocone. The remarkable length of the root under the paracone can be seen in buccal view. Measurements. LdP2 10.9; WdP2 6.6; LdP3 19.1; WadP311.2; WbldP3 5.3; LpdP3 6.9M LmdP3 7.2; LdP4 7.2; WdP3 13.0. KNM-FT 3614b (Fig. 3A, B) This is not the same individual as KNM-FT 3614a. The P3 was clearly a large, robust tooth suitable for bone-cracking and had a low mesiolingually set accessory cusp. The P4 is long and comparatively slender. It has a small cingulum mesial to the parastyle. There is a distinct, sharp parastyle and a large, sharp paracone. The metastyle is low and lingually convex. It gradually becomes lower distally. The protocone is set lingual to the parastyle with an embayment of the mesial part of the tooth between them. There are weak cingula mesiobuccally and lingually along the mesial half of the metastyle. The P4 of this specimen is practically indistinguishable from that of late Miocene hyaenids of the genus Hyaenictitherium and related forms. The only middle Miocene hyaenid that approaches this morphology is Thalassictis montadai (Villalta Comella & Crusafont Pairó 1943). The P4 of this species (Crusafont Pairó & Petter, 1969) appears more robust, lacks the anterior cingulum and has a straighter mesial face. These differences are small and I cannot exclude the possibility that this specimen represents a hyaenid. However, this would make it the oldest hyaenid specimen in Africa and in view of the demonstrated presence of Percrocuta at Fort Ternan I tentatively refer it to P. tobieni. Measurements. LP4 31.0; WblP4 10.3; LpP4 10.1; LmP4 12.1. KNM-FT 3614c A small, dumbbell-shaped M1 with a large, blunt paracone and somewhat smaller protocone. The metastyle shelf is almost entirely reduced and can be seen only as a very small widening of the distal border of the tooth just distolingual to the protocone. Measurements. LM1 7.4; WM1 20.9 KNM-FT 12693 This p3 forms a rounded rectangle in occlusal view. There is no distinct mesial accessory cusp, just a small swelling at the center of the mesial cingulum. The main cusp is worn. It is ovoid in occlusal outline and would have been pyramidal if unworn. The distal shelf is worn down and broken, so the presence and size of the distal accessory cusp cannot be determined. The distolingual shelf is large. Measurements. Lp3 14.0+; Wp3 9.3. KNM-FT 12694 A severely damaged tooth that can be identified as a p4 by the development of the distal shelf of the crown, which is clearly longer and better developed than the distal shelf of the p3 described above. Very little else can be said concerning the morphology of the tooth. Measurements. Lp4 16.2+; Wp4 9.8+. KNM-FT 12695 (Fig. 3 I-K). A mandibular corpus with dp3 and dp4 and an emerging m1. It also has alveoli for dp2, showing it to be two-rooted. No dp1 appears to have been present. The dp3 is a slender tooth with well developed mesial and distal accessory cusps and a sharply upturned distal cingulum cusp. The main cusp is short and has a sharp tip. The dp4 is morphologically very similar to KNM-FT 3362, described above, but the metaconid is relatively slightly smaller. Measurements. Ldp3 13.5; Wdp3 5.7; Ldp4 15.8; Wdp4 6.3. KNM-FT 14140 This p3 is broken mesially and distally, so the development of the accessory cusps is not clear, although the mesial one must have been quite small and the distal one situated in a short shelf. The main cusp is pyramidal. Measurements. Lp3 14.7+; Wp3 9.5. DISCUSSION This material can be assigned to Percrocutidae on the basis of several features, most important of which is the morphology of the deciduous fourth premolar (dp4). This tooth was shown by Chen & Schmidt-Kittler (1983) to differ from the homologous tooth of Hyaenidae in the following: The metaconid is set distal to and well separate from the protoconid; the talonid is very short; and the talonid cusps are restricted to small buds at the distal end of the tooth. In Hyaenidae, on the other hand, the metaconid is set only slightly distal to the protoconid and appressed to it (in derived Hyaenidae such as Crocuta the dp4 metaconid is lost); the talonid is long; in primitive Hyaenidae (e.g., Hyaenictitherium), there are distinct entoconid and hypoconid and commonly a third cusp that may be an entoconulid; and in derived Hyaenidae only the entoconid is distinct. The Fort Ternan material includes two dp4 that both match the morphology of dp 4 in Percrocutidae. In addition to these features, all of the Fort Ternan percrocutid specimens are considerably more derived than contemporaneous Eurasian Hyaenidae, which at that time (ca MN 6 or early MN 7/8 depending on opinion in the European mammal zonation) were confined to small, omnivorous forms such as Protictitherium and Plioviverrops (Turner et al. 2008): type 2 hyenas in the classification of Werdelin & Solounias (1996). Percrocuta tobieni was described from the middle Miocene of the Ngorora Formation (Crusafont Pairó & Aguirre 1971). Finds from this formation are dated to approximately 12.5-11 Ma (Morales & Pickford 2005), i.e., somewhat younger than Fort Ternan. To the extent that they overlap, the Fort Ternan material does not differ in any substantial way from the Ngorora Formation material. Therefore, despite some minor differences, e.g., in the relative length of the m1 talonid, assigning the Fort Ternan material to P. tobieni appears justified. This is in agreement with, e.g., Morales & Pickford (2006), in which the faunal list for Fort Ternan includes P. tobieni as one of a number of taxa shared with the Ngorora Formation. This makes the Fort Ternan record the oldest of this species. Thus, the taxonomic home of the Fort Ternan percrocutid is clear. However, the material is of considerable interest because it includes both lower and upper dentitions, including lower and upper deciduous teeth. This not only is the first instance of associated upper and lower deciduous teeth in Percrocutidae, but these upper deciduous teeth are the first known for Percrocutidae and allow for a consideration of the full percrocutid dentition. The following is a comparison of the deciduous upper dentition with that of Hyaena hyaena, discussed and illustrated in Baryshnikov & Averianov (1995). Percrocuta tobieni and H. hyaena share a similar overall structure of the deciduous dentition, so the differences are all in the details, none of which are as revealing as the dp4. All the observations made are confirmed by the deciduous upper dentition of C. crocuta although the latter is more reduced and hypercarnivorous than that of either P. tobieni or H. hyaena. dP2 This tooth is relatively larger and more robust in P. tobieni. In particular, the mesial end is broader and has a more distinct mesial accessory cusp in P. tobieni. In both taxa the tooth has a marked lingual bulge, however, this bulge is set further mesially in P. tobieni, in which the maximum width is attained directly lingual to the apex of the main cusp, whereas in H. hyaena it is set lingual to the notch between the main cusp and the distal accessory cusp. In contrast to the mesial accessory cusp, the distal one is more developed in H. hyaena than in P. tobieni. dP3 The preparastyle is of similar size relative to the whole tooth in the two taxa but the cusp of the preparastyle in P. tobieni is distinctly transversely extended. In P. tobieni the parastyle is more prominent, triangular, and set distinctly lingual to the long axis of the paracone. In H. hyaena this cusp is less developed, round and set closer to the paracone. The paracone and metastyle are similar in the two taxa, but they differ in the position of the protocone. In P. tobieni the protocone is centered lingual to the notch between parastyle and paracone, whereas in H. hyaena the protocone is set lingual to the apex of the paracone. This obviously reflects a difference in the position of the lingual root of the dP3. dP4 The dP4 of P. tobieni is more buccolingually extended than the dP4 of H. hyaena This means that the dP4 of the extant species is more triangular in occlusal outline that it is in P. tobieni. The dP4 of P. tobieni has a larger protocone and a more bowed distal edge than dP4 of H. hyaena. Upper dentition The permanent upper dentition of P. tobieni, previously unknown, presents no remarkable features, except one: that it is practically indistinguishable from that of late Miocene Hyaenidae such as Hyaenictitherium or Lycyaena. In particular, it does not share with other, more derived Percrocutidae the reduced and distally shifted protocone of P4, an observation that has consequences for our understanding of the evolution of the family.Published as part of Werdelin, Lars, 2019, Middle Miocene Carnivora and Hyaenodonta from Fort Ternan, western Kenya, pp. 267-283 in Geodiversitas 41 (6) on pages 270-274, DOI: 10.5252/geodiversitas2019v41a6, http://zenodo.org/record/369995
Myacyon peignei Werdelin 2019, n. sp.
No full text? Myacyon peignei n. sp. (Fig. 1) Small amphicyonid – Shipman et al. 1981: 64. Agnotherium sp. – Morales & Pickford 2005: 276. — Werdelin & Simpson 2009: 782. — Werdelin & Peigné 2010: 605. Myacyon sp. I – Morales et al. 2016: 145. HOLOTYPE. — KNM-FT 3611, left P4 (Fig. 1 A-C). ETYMOLOGY. — Honoring the memory of Stéphane Peigné and his achievements in the field of carnivore paleontology. LOCALITY. — Fort Ternan (type locality) only. STRATIGRAPHIC RANGE. — Middle Miocene; upper Serravallian; 13.7-13.8 Ma (Pickford et al. 2006). MATERIAL EXAMINED. — KNM-FT 3379, left m1; KNM-FT 3399, right M1; KNM-FT 3611, left P4. Judging by size and morphology, all three specimens represent the same taxon, but not the same individual, given their differing states of wear. The identity of this taxon has been discussed several times in the past 15 years. In 2005 Morales & Pickford described the species Agnotherium kiptalami Morales & Pickford, 2005 based on a cranium from the Middle Miocene of Kabarsero, Ngorora Formation, Tugen Hills, Kenya. At the same time, they also discussed the Fort Ternan specimens, attributing them to Agnotherium, but without assigning them to species. The attribution to Agnotherium was followed by Werdelin & Simpson (2009) and Werdelin & Peigné (2010). More recently, Morales et al. (2016) revised the Amphicyonidae of Africa. In so doing they transferred A. kiptalami to Myacyon Sudre & Hartenberger, 1992, tentatively suggesting that the Fort Ternan specimens might also belong in that genus. DIAGNOSIS. — Amphicyonidae of moderate size. P4 short and broad with protocone shelf well developed and extended distally to the metastyle. M1 protocone shelf short mesiodistally. m1 hypercarnivorous with low paraconid and tall protoconid. Small metaconid present, appressed to distolingual part of protoconid and jutting out distally from it. Talonid short. DESCRIPTION KNM-FT 3379 (Fig. 1 D-F). This m1 is relatively tall for its length. The paraconid is low and short with robust and slightly worn pre- and postparacristids. The paraconid is much smaller than the protoconid in all dimensions. The protoconid, which is nearly unworn, is tall and trenchant with salient pre- and postprotocristids and a sharp apex. The metaconid is small and located at the distal end of the protoconid, appressed to it and jutting out distally. The talonid is broken distally but has a substantial hypoconid and cristid obliqua and a very low but nevertheless distinct entoconid. In occlusal view the lingual side has a wavy outline, bulging out at the center of the trigonid and between the protoconid and talonid, whereas the lingual side is convex throughout. There is a weak lingual cingulum that runs from the protoconid to the mesial end of the metaconid. Measurements. Lm1 c. 21; Wm1 10.2; Ltm1 14.0. KNM-FT 3399 (Fig. 1 G-H) This M1 has large paracone and metacone and a mesiodistally shortened lingual shelf that is worn nearly flat. In occlusal view the paracone is slightly larger than the metacone and in distal view it can be seen to be considerably taller. Both cusps are broad and pyramidal. There is a very small cusp located at the base of the lingual side of the paracone. The lingual shelf shows a crest-like, low hypocone, but the protocone cannot be discerned at all. The tooth is too worn for the development of the cingula to be determined with certainty. Measurements. LM1 16.8; WM1 c. 20.5. KNM-FT 3611 (holotype, Fig. 1 A-C) Like the m1 this P4 is relatively short and tall and nearly unworn. There is a low parastyle cusp that is closely appressed to the paracone. The paracone is tall and trenchant. The metastyle is of about the same length as the paracone, but considerably lower and lacks a distinct cusp. The protocone is very low and set in a large shelf that extends from the parastyle cusp to the mesial end of the metastyle, reminiscent of the morphology of some Lutrinae. This shelf continues as a lingual cingulum to the distal end of the metastyle. Measurements. LP4 22.9; WaP4 15.1; WblP4 9.3; LpP4 9.2; LmP4 9.0. DISCUSSION The specimens described above cannot be attributed to any named species of Amphicyonidae. Therefore, a new species is indicated, a conclusion also reached by Morales et al. (2016). Generic attribution is, on the other hand, a very complicated and unresolved issue. The material was attributed to Agnotherium by Morales & Pickford (2005), Werdelin & Simpson (2009), and Werdelin & Peigné (2010). Agnotherium is, however, a poorly characterized genus, despite work by, e.g., Kuss (1962). Morales et al. (2016) present sound arguments why the Fort Ternan material cannot be attributed to that genus and they tentatively assign the material to Myacyon Sudre & Hartenberger, 1992. This is not an implausible attribution, but the holotype (and only specimen) of the type species, Myacyon dojambir, is a severely damaged distal half of a mandible corpus with m1 and damaged m2. The illustrations of this material in Sudre & Hartenberger (1992) are, in addition, entirely inadequate and their published measurements confusing. The verbal description by Sudre & Hartenberger (1992: 554) fits the Fort Ternan m1 quite well but is fairly general and the only truly distinctive character is the distally positioned metaconid. A distinctive feature of the Fort Ternan P4 is the development of the protoconid shelf, but this feature is not known in Myacyon, including ‘ Agnotherium ’ kiptalami (also reassigned to Myacyon by Morales et al. [2016]). This protocone shape bears some resemblance to a specimen from Frohnstetten, Germany attributed by Kuss (1962: fig. 5c) to Agnotherium antiquum; however, that specimen is broken and its actual shape cannot be definitively determined. In summary, I here attribute the material to? Myacyon peignei n. sp. in anticipation of more material that can definitively clarify the generic attribution.Published as part of Werdelin, Lars, 2019, Middle Miocene Carnivora and Hyaenodonta from Fort Ternan, western Kenya, pp. 267-283 in Geodiversitas 41 (6) on pages 268-269, DOI: 10.5252/geodiversitas2019v41a6, http://zenodo.org/record/369995
The taxonomy and taphonomy in mio-pliocene and late middle pleistocene micromammals from the Cape west coast, South Africa
No full textIncludes bibliographical references.The study sites investigated in this thesis are situated along the southwest coast of South Africa in an area dominated by the sclerophyllous fynbos of the Strandveld and Sandveld, which supports a well-known micromammal (murid, soricid, macroscelid, bathyergid and chrysochlorid) fauna. This study presents the results of a taphonomic, taxonomic and palaeoecological study of micromammal assemblages from two palaeontological sites in the Saldanha Bay/Langebaanweg area on the west coast, in the western Cape Province, South Africa. The micromammalian populations of these two sites are compared both taxonomically, and taphonomically, with other fossil sites on the west coast dating to the Terminal Pleistocene and Holocene. The older of the two sites is 'E' Quarry at Langebaanweg. a disused phosphate mine, which is the only site in the western Cape Province representing the Mio-Pliocene, a slice of time when modem micromammal genera were emerging. The second site investigated in this thesis is the late Middle Pleistocene site of Hoedjiespunt 1, which fills a significant gap in the continuum of micromammal evolution in the western Cape. This site contained faunal remains accumulated by a brown hyaena (Hyaena brunnea), and micromammal bones and teeth were recovered from the same sediments. The Hoedjiespunt 1 micromammal assemblages have added to the information available on the past distribution of several species in the Saldanha area, and have confirmed the presence of several endemic species in the west coast area during the late Middle Pleistocene. A comparison between the other west coast fossil sites and Hoedjiespunt 1 indicates that conditions on the west coast in the late Middle Pleistocene were relatively more arid. The micromammals from Langebaanweg 'E' Quarry indicate that fynbos microhabitats were well established during the Mia-Pliocene on the west coast. Both the fynbos, and most of the micro mammal genera present at LBW, have families resident in the west coast area today. The micromammal assemblages from Langebaanweg indicate that the general micromammal population in the area remained relatively unchanged during the period of deposition of the two main fossil-bearing members of the Varswater Formation. There is no compelling evidence to suggest that any marked climatic or environmental change took place during this period
The Rodent assemblages from the late Aragonian and the Vallesian (middle to late Miocene) of the Vallès-Penedès basin (Catalonia, Spain)
No full textConsultable des del TDXTítol obtingut de la portada digitalitzadaLa conca del Vallès-Penedès es una àrea clau per a l'estudi de les successions de mamífers del Miocè europeu, donat que el seu abundant registre cobreix gairebé la totalitat d'aquest període. Recentment, degut a les obres d'ampliació de l'Abocador de Can Mata (ACM), al terme municipal de Els Hostalets de Pierola (l'Anoia, Barcelona), el nombre de jaciments coneguts de micro- i macromamífers s'ha duplicat. L'estudi de les faunes de micromamífers de la sèrie estratigràfica de l'ACM ha permès aportar importants dades bioestratigràfiques per a la definició de les biozones MN 7 i MN 8, actualment basades en localitats aïllades de França i Alemanya. També es proposa una correlació bioestratigràfica amb altres conques ibèriques com Calataiud-Terol. Pel que fa als rosegadors de la sèrie de l'ACM, es descriu una nova espècie de castòrid: Chalicomys n. sp. Aquesta espècie ja presenta un mode de locomoció aquàtica molt similar al del castor actual. Durant les obres d'ampliació de l'ACM es localitzà un nou jaciment, Barranc de Can Vila 1 (BCV1), que, a més d'una abundant mostra de micro- i macrofauna, ha lliurat un esquelet remarcablement complet d'una nova espècie de gran antropomorf: Pierolapithecus catalaunicus. L'estudi dels rosegadors de BCV1 ha permès situar cronològicament aquesta localitat a la part baixa de la MN 7+8, entre els 12,5 i els 12 Ma. En conseqüència aquesta localitat representa el registre més antic dels grans antropomorfs a la Península Ibèrica. L'estudi tafonòmic de les restes recuperades a BCV1 revela que diferents agents tafonòmics estigueren involucrats en la gènesi de l'acumulació. Es reconeix la depredació com el principal agent d'acumulació en el cas de l'individu de primat. Per contra l'acumulació de la majoria de la resta de fòssils no sembla estar associada a l'acció de depredadors i/o carronyaires. La fauna de micromamífers de BCV1 ens indica la presència d'un ambient forestal subtropical i humit en oposició a l'ambient clarament més sec i obert imperant a les conques de l'interior d'Espanya. Aquest fet podria explicar l'absència d'antropomorfs a aquestes àrees durant el Miocè. Seguidament es compara la composició i estructura de la taxocenosi de rosegadors de l'Aragonià terminal i del Vallesià de la conca del Vallès-Penedès amb la dues conques ibèriques (Calataiud-Terol i Duero). Els resultats dels anàlisis estadístics multivariants mostren que les paleocomunitats de rosegadors de la conca del Vallès-Penedès són marcadament diferents de les de les conques de l'interior d'Espanya durant la major part de l'interval de temps considerat. L'ambient al Vallès-Penedès sembla que fou més humit i boscós, assimilant-se a l'existent a zones més septentrionals. Al límit entre el Vallesià Inferior i el Superior (vers fa 9,7 milions d'anys) les paleocomunitats de rosegadors canvien bruscament a totes les conques. Aquest període és testimoni d'un canvi vers a associacions menys diverses i dominades per un o uns pocs gèneres. La diferenciació biogeogràfica existent a la Península Ibèrica es manté i fins hi tot incrementa durant el Vallesià Superior. Aquest canvi abrupte es coneix com la Crisi Vallesiana i també afectà a les comunitats de macromamífers, implicant en ambdós casos l'extinció de formes pròpies del Miocè Mitjà adaptades a ambients càlids i boscosos i resultant en un descens en la diversitat. Mitjançant diferents tècniques es mostra que aquest esdeveniment d'extinció no es va estendre a altres àrees d'Europa, on la diversitat es va mantenir estable o fins hi tot va incrementar.The Vallès-Penedès Basin is a crucial area for the study of the mammal succession of the European Miocene, since its abundant record covers nearly the totality of this period. Recently, thanks to the extension works of a rubbish dump, the so-called «Abocador de Can Mata» (ACM) at Els Hostalets de Pierola (l'Anoia, Barcelona), the number of known micro- and macromammal sites has doubled. The study of the micromammal faunas of the stratigraphic series of the ACM has added important data for the definition of the biozones MN 7 and MN 8, which now are based in isolated sites from France and Germany. We have also proposed biostratigraphic correlation for the Late Aragonian of the Vallès-Penedès Basin to other Iberian basins such as Calatayud-Teruel. Concerning the rodents of the ACM series, a new species of castorid is described: Chalicomys n. sp. This species already shows a mode of aquatic locomotion very similar to that of the extant beaver. A new site which has yielded an abundant sample of micro- and macrofauna, Barranc de Can Vila 1 (BCV1), was discovered during the extension works of the ACM. This site has also provided a remarkably complete skeleton of a new species of great ape: Pierolapithecus catalaunicus. The study of the rodents of BCV1 allows us to chronologically place this site in the lower part of MN 7+8, that is between 12.5 and 12 Ma. Accordingly this locality represents the oldest record of great apes in the Iberian Peninsula. The taphonomical study of the remains recovered at BCV1 reveals that different taphonomical agents were involved in the origin of the accumulation. Predation is recognized as the main accumulation agent in the case of the primate individual. In contrast, the accumulation of the rest of the fossils does not seem related to the action of predators and/or scavengers. The micromammal fauna from BCV1 indicates the presence of a humid subtropical forest environment as opposed to the clearly dryer an more open environment dominant in inner Spanish basins. This fact may account for the absence of great apes in those areas during the Miocene. Straight after that the composition and structure of rodent taxocenosis from the latest Aragonian and the Vallesian of the Vallès-Penedès Basin is compared with those of two Iberian basins (Calatayud-Teruel and Duero). The results of the multivariate statistic analyses show that the rodent paleocommunities of the Vallès-Penedès are markedly different from those of the inner Spanish basins during most of the considered time span. The environment in the Vallès-Penedès Basin appears to have been more humid and forested, being similar to that occurring at higher latitudes. At the Early/Late Vallesian boundary (at 9.7 Ma) an abrupt change in the rodent paleocommunities of all the basins is recorded. This period witnesses a shift towards lower-diversity faunas dominated by one or a few genera. The biogeographic differentiation existing in the Iberian Peninsula is retained and even increases during the Late Vallesian. This abrupt change is known as the Vallesian Crisis and also affected the macromammal communities, implying in both cases the extinction of forms of characteristic of the Middle Miocene and adapted to warm forest environments. That ultimately resulted in a decrease of diversity. By the means of different techniques we show that this extinction event did not affected other areas of Europe, where diversity remained stable or even increased
Perioperative patient outcomes in the African Surgical Outcomes Study: a 7-day prospective observational cohort study
No full textRevision de los mamíferos bunodontos de tipo nutria del Mio-Plioceno del Subcontinente Indio
No full textA revision of the Enhydriodontini of the Indian Subcontinent is undertaken on the basis of previously described and recently collected bunodont otter-like fossils from the sub-Himalayan Siwalik Group. It is confirmed that, with the passage of geological time spanning the period 13 – 3 Ma, there occurred a progressive increase in body size, a reduction of the anterior part of the premolar row and an increase in degree of cheek tooth bunodonty and cusp mastoidization. Functional analysis of a snout with a partly preserved incisor battery of Enhydriodon sivalensis, reveals that it was probably a molluscivore, preying principally on bivalves, while other species of enhydriodonts were more likely to have been piscivores and cancrivores. One new species of Sivaonyx is described from the base of the Late Miocene of Pakistan. Bunodont otter-like mammals from Eurasia, Africa and North America are briefly discussed in light of the revision of the Indo-Pakistan ones. The origins and phylogenetic relationships of these mammals remains obscure. The major differences in dental anatomy indicate that these Old World otter-like mammals should not be classified in Enhydrini, but in a tribe of their own Enhydriodontini new tribe.La revisión de los Enhydriontinos del subcontinente Indio se aborda, tanto en base a los fósiles de nutrias bunodontas previamente descritos, como a los hallazgos recientemente realizados en el Grupo de los Siwaliks en el sub-Himalaya. Se confirma que durante el período de tiempo comprendido entre los 13 a 3 Ma hubo un progresivo incremento en la talla corporal, una reducción de la parte anterior de la serie premolar y un incremento en el grado de bunodoncia y mastoidización de las cúspides de los dientes. El análisis funcional de un hocico de Enhydriodon sivalensis con la batería de incisivos parcialmente conservados revela que esta especie fue parcialmente malacófaga, alimentándose principalmente de bivalvos, mientras que otras especies de enhydriontinos fueron más piscívoras y cancrívoras. En el trabajo también se describe una nueva especie de Sivaonyx procedente de la base del Mioceno Terminal de Paquistán. Los mamíferos bunodontos de tipo nutria de Eurasia, África y América del Norte son brevemente discutidos a la luz de la revisión realizada para las formas paquistaníes. El origen y relaciones filogenéticas de estos mamíferos permanecen oscuros. Las importantes diferencias en anatomía dental indican que estos mamíferos de tipo nutria del Viejo Mundo no deberían ser clasificados como Enhydrini, sino en una tribu propia, Enhydriodontini nueva tribu
