Cainozoic Research, 4(1-2), pp. 41-49, February 2006
Latest Miocene Myliobatids (Batoidei, Selachii) from the
Alvalade Basin, Portugal
² Miguel Telles+Antunes¹ & Ausenda Cáceres+Balbino
1 Centro de Estudos Geologicos, Faculdade de Ciencias e Tecnologia (UNL)/ Quinta da Torre 2829-516 Caparica, Portugal.
e-mail: [email protected]
2 Departamentode Geociencias, Universidade de Evora, Apartado 94, 7002-554 Evora, Portugal, e-mail: [email protected].
Received 5 April 2003; revised version accepted 12 January 2005
Myliobatid teeth from the EsbarrondadoiroFormation(Alvalade Basin, Portugal) are described. These teeth have been attributed to the
Aetobatus A. cf. and Other teeth genera (represented by cappettai n. sp.), Myliobatis (M. aquila) Pteromylaeus (P. sp.). Myliobatid are
from extinct whose taxonomic remains unresolved. an genus status
colhidos da de de São descritos dentes de Myliobatidae em depósitos Formacão Esbarrondadoiro (Bacia Alvalade), dos géneros Aetoba-
cf. Outros tus (representado por Aetobatus cappettai, nov. sp.), Myliobatis (M. aquila) e Pteromylaeus (P. sp.). dentes, pertencentes a
ainda esclarecida.. géneros extintos, são de posição taxonómica não
Key words: Myliobatidae, Alvalade Basin, Miocene, new species.
Introduction sence ofthe extant great white shark, Carcharodon carcha-
Pliocene rias Linne, 1758, that was more common in than
The Alvalade basin its differentiationin (Portugal) began the at the time declining Carcharocles megalodon Agassiz, Miocene times. A horst the lower Alentejo region in Late 1843. Teeth of C. carcharias too to are large pass unno- of Paleozoic rocks (the Valverde horst) composed sepa- ticed after washing and sieving of tons of sedimentsfrom rated this from the much lower depression larger Tagus the EsbarrondadoiroFormation. Thus, a somewhat older
basin (Antunes, Mein & Pais, 1986). Subsidence allowed than Pliocene age is inferredfor the Esbarrondadoirofauna successive marine The older two transgression events. which is compatible with the mammal-based. Latest Mio-
event is probably correlated to the lowerpart ofthe Cacela indications. The selachian fauna is rich in cene age taxa Formation in the Algarve, of Late Tortonian as age, sug- and in specimens. It is the most modern among Miocene the mollusc fauna. The second gested by corresponding faunas fromEurope (Balbino, 1995; Antunes etal., 1999;
event is marked by the deposition ofmostly sandy, micro- B albino & Cappetta, 2000). This paper deals with one of sediments in fossil-poor (occassionally pelitic some areas) the main batoid families from the Alvalade Basin, the
of the Esbarrondadoiro Formation.The Esbarrondadoiro Myliobatidae.
Formation yields molluscs, a rich marine fish fauna and
rare freshwater fishes (Antunes et ah, 1995), chelonians
(Trionyx), marine mammals and (in the same beds) a few Material land mammals: mastodont, Hipparion and remnants of
other larger mammals, as well as lagomorphs, rodents and
insectivores (Antunes, 1984; Antunes, Mein & Pais, 1986; All material is from three outcrops of the Esbarrondadoiro
Smallmammals indica- Formationin Alvaladebasin Antunes & Mein, 1989, 1995). are the (Baixo Alentejo Province,
tive of the MN13 zone (Late Turolian, ca 5-6 Ma). This Southern Portugal). These are: SantaMargarida, Esbarron-
age more or less corresponds to the Messinian (Latest Mio- dadoiroand Vale de Zebro (see Balbino & Cappetta, 2000
cene). The marine fish fauna of the EsbarrondadoiroFor- for further details). The Formation is of Late Miocene
mationclearly differs from fish faunas ofPlioceneage from (Messinian) age and also assigned to the MN13 mammal-
SE Spain (as one of us, M.T.A., couldobserve in material zone (Late Turolian). Based on magnetostratigraphy an age
from the Elche area) and Belgium (Antunes, 1978; Cap- between 5.3 and 5.8 Ma has been inferredfor these depos-
petta, 1987). The most evident difference lies in the ab- its. -42- -43-
All specimens are from Esbarrondadoiro (Baixo Alentejo Province, Portugal), collected in the Late Miocene Esbarrondadoiro Formation by the authors. -44-
1-8. Aetobatus Antunes & lower dentition. 1 -Incom- Figures cappettai Balbino,nov. sp.: (1-4) upper dentition,(5-8) (mandibular)
tooth: labial occlusal - plete a, view; b, lingual view; c, view; d, basal view; e, profile. 2 holotype (SEV 20), incomplete tooth : a, labial
view; b, lingual view; c, occlusal view; d, basal view; e, profile. 3 - Incomplete tooth: a, labial view; b, lingual view; c, occlusal view; d,
basal view. 4 - Nearly complete tooth: a, occlusal view; b, basal view. 5 - Incomplete tooth: a, occlusal view; b, basal view; c, profile, 6
- Nearly complete tooth: a, occlusal view; b, basal view. 7 - Incomplete tooth: a, occlusal view; b, basal view. 8 - Incomplete tooth: a,
occlusal view; b, basal view.
Institutionalabbreviations - Figures 1-8
MP Paleontology Laboratory, Universite de Montpellier Holotype - SEV 20 Figures 2a-e. Type locality: Esbarron-
II, Montpellier, France; dadoiro in the Alvalade basin. Southern Portugal. Stratum
SEV Palaeontological Collections, Evora University, typicum: Esbarrondadoiro Formation, Alvalade basin
Evora, Portugal. (Baixo Alentejo Province, SouthernPortugal); Latest Mio-
cene, late Messinian or MN13 mammal-zoneon the basis
of the small mammals from the same beds (corresponding
Systematic palaeontology to Late Turolian); magnetostratigraphic age, ca 5.3 to 5.8
Ma.
Class Chondrichtyes Huxley, 1880
Subclass Elasmobranchii Bonaparte, 1838 Othermaterial studied- Santa Margarida (7 teeth), Esbar-
Superorder Batomorphii Cappetta, 1980 rondadoiro (258 teeth) and Vale de Zebro (51 teeth).
Order Myliobatiformes Compagno, 1973
Superfamily Myliobatoidea Compagno, 1973 Derivatio nominis - The species name is dedicated to Dr.
Jordan, 1888 Henri-Charles renowned Family Myliobatidae Cappetta (Montpellier), a pa-
leoichthyologist whose collaboration we have greatly ap-
preciated.
The family Myliobatidae comprises the following extant
Aetobatus - teeth genera: Blainville, 1816, Aetomylaeus Carman, Diagnosis Upper narrow, long, slightly convex;
1908, Myliobatis Cuvier, 1817 and Pteromylaeus Carman, crown low, thickened in the central part; lateral extremities
1913 (see Bigelow & Schroeder, 1953;Compagno, 1973). prominent; root higher than crown, decreasing in height
Nishida included in (1990) this family the genera Rhinop- from the centre to the edges; blades on the labial face are
tera Cuvier, 1829, Mobula (Rafinesque, 1810) and Manta almost smooth, lacking marked grooves; grooves on the
Bancroft, 1828, but excluded Pteromylaeus. Nelson (1994) lingual face very marked, they persist almost to the crown;
subdivided the family Myliobatidae into the subfamilies basal surface of the root with narrow, deep grooves as well
Mobulinae Mantaand Mobula), Aetobatus as all of the same lower teeth arched and ( Myliobatinae ( , blades, width;
and and basal Aetomylaeus, Myliobatis Pteromylaeus) Rhinop- labially convex, extremely flat; angle ca 30°, with
terinae (Rhinoptera). Other myliobatid genera are only very oblique basal face; root high, thinning from the central
known from the fossil record; Apocopodon Cope, 1885, part to the lateral edges; blades wide and separated by
Brachyrhizodus Romer, 1942, Garabatis Cappetta, 1993, deep, wide grooves.
Igdabatis Cappetta, 1972, Lophobatis Cappetta, 1986,
Leidybatis Cappetta, 1986 and PseudoaetobatusCappetta, Description - The upperand lower teeth are notably differ-
1986. The tooth morphology of all these genera is signifi- ent. The upper teeth are narrow, long and slightly convex. cantly differentfrom thatofotherbatoids. Its dentitionis of The crown is low and thicker in its central part. Lateral the crushing type. The medial teeth are broad, juxtaposed extremities are prominent; in occlusal view, the lateral ex-
intorows and forming (entirely or as the larger part) a den- tremities constitute a lateral border that is not affected by tal Medial teeth flanked 3 that abrasion. The face of the is plate. are by (at most) rows vertical, lingual crown sepa- become progressively smaller towards the commissure. In rated from the root by a thin edge. The root is thicker than
some Myliobatidae with a very specialized dentition, the the crown; the thickness regularly decreases from the cen-
lateralrows are much reduced or even lacking, whereas the tral part towards the borders (in lateral view). The basal medial row became progressively broader and may even surface presents alternating (narrow and shallow) grooves
constitute the whole dental plate (as in Aetobatus). The and blades. Width is the same in all blades, whose basal
dental is of the in surface is flat. The tooth’s section is root polyaulacorhize type, except some labio-lingual nearly
genera where the very lateral rows of teeth have roots of straight. The arched lower teeth are labially convex. The the holaulacorhiza type. Myliobatids (also known as as slightly oblique lingual and labial faces of the crown are
labial face of each tooth is angel-fishes) live in coastal, shallow, tropical to warm tem- parallel. The superimposed on
the constitutes under which the perate waters. root. It a prominent edge,
lingual border of the next tooth is located. This kind of
root teethassociation results in a dental plate. The is thick,
Genus Aetobatus Blainville, 1816 but thickness diminishes towards the lateral borders. The
than blades are broader those ofthe upper teeth roots. They
Aetobatus cappettai n. sp. are separated by broader and deeper grooves. -45 -
9-12. cf. 9 - lower tooth: labial Figures Myliobatis aquila (Linne, 1758). Probably (mandibular) median a, view; b, lingual view; c,
basal view. 10 - Upper median tooth; a, labial view; b, lingual view; c, basal view; d, occlusal view. 11 - Lateral tooth: occlusal
view. 12 - Lateral tooth: occlusal view. -46-
13-18. 13 - Median tooth; labial and lateral occlusal view. Figures Pteromylaeus sp. a, view; b, lingual view; c f, views; d. basal view; e, - 14 - Median tooth: a, labial view; b, lingual view; c, basal view. 15 Median tooth: a, labial view; b, lingual view; c, occlusal view.
16 - Lateral tooth: a, lateral view; b, basal view. 17 - Lateral tooth: profile view. 18 - Lateral tooth: lateral view. -47-
Figures 19-25. Myliobatidae indet. 19-Median tooth: a, labial view; b, lingual view;c, occlusal view; basal view. 20 - Median tooth: a,
labial view; b, occlusal view; c, basal view. 21 - Median tooth: a, labial view; b, lingual view; c, occlusal view; d, basal view. 22-25
- Lateral teeth: occlusal views.
Differentiation — Compared to Aetobatus irregularis dadoiro (875 teeth) and Vale de Zebro (54 teeth)
Agassiz, 1843 (MP collection sample number RON 34,
Paris coll. - The median teeth 30 Late Eocene, Ronquerolles, Basin, MP; (Cap- Description are elongate, attaining petta, 1986) the teeth of the new species are more arched mm in length. Lateral teeth are much smaller. In occlusal and the width of the crown is not constant. In A. irregu- view, the crown is more laterally developed than labio- laris, the lower teeth are only slightly arched and their lingually. The nearly rhombic outline in occlusal view is width is the bent lin- bounded latero-anterior borders. constant, root being only slightly by concave The very
has less arched lower teeth then A. gually. The new species prominent lingual edge clearly superposes the trilobate arcuatus Agassiz, 1843 (Langhian, Loupian, Southern root. Labial face is high, the lingual face is very short.
France, coll. MP). The labial and lingual faces of the root
are oblique and prominently developed, the basal angle is Discussion - Leriche (1910: 252) described in detail one
of is form attributed ca40°. The oblique root of the upper teeth A. arcuatus that he to the extant species Myliobatis
less lingually elongated. Aetobatus cappettai nov. sp. is aquila. Cappetta & Nolf (1991: 62) attributed a single lat-
similar to A. narinariEuphrasen, 1790 (Red Sea, MP REC eral tooth to M. aquila. The studied teeth, and especially
42), but differs from it by the inclination of the labial and the lateral teeth are very similar to those of M. aquila.
lingual faces of the crown, the thickness of the lingual However, the range of morphological variation within the edge, the inclinationofthe root, the shape ofthe blades and teethof Myliobatidae makes a certainidentificationimpos- of the well the basal sible. grooves, as as angle.
Genus Myliobatis Cuvier, 1817
Genus Pteromylaeus Garman, 1913
Myliobatis cf. aquila (Linné, 1758)
Figures 9-12
Pteromylaeus sp.
Materialstudied — Santa Margarida (47 teeth), Esbarron- Figures 13-18 -48-
Material studied - Santa (15 teeth), Esbarron- with Margarida together a fourthunidentifiedmyliobatid make up the dadoiro (179 teeth) and Vale de Zebro (77 teeth). myliobatidae faunaof the Late Miocene Esbarrondadoiro
Formation in Alvalade basin (Portugal). Aetobatus cappet-
- The is Description genus Pteromylaeus represented by tai n. sp. is introducedfor theAetobatus material.The very
very thick teeth fragments. The crown is thick (the thick- broad dentalvariationin Myliobatis and Pteromylaeus does ness diminishes laterally), with a plate, but with irregular not allow identificationof isolated, often damaged teeth at occlusal surface. The vertical lingual face presents a dis- the species level. tinct ornamentation, and an edge that is separated from the
crown a well-marked furrow. The labial surface, also by SantaSanta Esbarron- ValeVale de TotalTotal
vertical, is ornamented. The root is lingually inclined. Margarida dadoirodadoiro ZebroZebro
Aetobatus 77 258 5151 316316 Blades and grooves are well marked, almost untilthe ante- rior end cappettain. sp.sp. (close to the edge). The posterior extremities are Myliobatis 47 875 54 976976 free, so the posterior border is irregular. The lateral teeth cf. aquila are much smaller. Theiroutline is 6 polygonal (4 or sides) 1515 179179 77 271 Pteromylaeus sp. 271 in occlusal view. The crown (although affected by abra- Myliobatidae -- 6363 - 6363 sion) is shorter than the root, which is mesio-distally indet. TotalTotal it has 2 6969 1375 182 1626 lengthened; to 4 blades. Grooves are deep but do not attain the lingual edge. Table 1. Studied material
Discussion - The teeth described may be assigned to
Pteromylaeus by their morphologic characters. However, cf. Myliobatis aquila (Linne, 1758) is the most common their incomplete nature as well as the lack of teeth in asso- in the studied myliobatid species material, making up ca ciation prevents us to reach their determinationat the spe- 60% of the specimens. Aetobatus cappettai n. sp. (19%)
cies’ level. and Pteromylaeus sp. (17%) are also common species.
Myliobatidae indet. (4%) are rare, and restricted to the lo-
cality ofEsbarrondadoiro. The relative abundancesof the Myliobatidae indet. three identifiedMyliobatid species among the three locali- Figures 19-25 ties are broadly similar, with the exception ofMyliobatis
cf. aquila that is underrepresented in the locality ofVale de
Material studied - Esbarrondadoiro (63 teeth). Zebro. Densities of Myliobatid teeth are especially low in
the Santa The Margarida outcrop. sedimentology indicates
- The small median teeth are in Description hexagonal that Esbarrondadoiro sediments were deposited in deeper outline. The enameled occlusal surface a middle presents waters than the Santa Margarida more littoral, higher- The face has cutting edge. high lingual a granular ornamen- where energy ones molluscs would be less common, possi- tation and The labial and a cutting, prominent lingual ridge. bly explaining the lower abundance of molluscivorous borders The is close lingual are near parallel. crown larger Myliobatids in the last locality. to the marginal angles than at its base. The separation be- tween the crown and the root inthe lingual face is made by
rounded border. The is lower than the a prominent, root Acknowledgements and about 12 blades that crown presents are separated by
The root's thickness diminishes from the deep grooves. This work results fromresearch concerning the Line n° 1 of central towards the lateral borders. The lateral teeth part the Centro de Estudo Geologicos ofthe UniversidadeNova are smaller than the median ones. The crown is high; abra- de Lisboa, as well as the PRAXIS XXI 2/2.1/ CTA/ 106/ sion results in a plate, grossly lozengic, mesio-distally 94 Project “Neogenico e Quatemario da Margem atlantica lengthened area. The labial ridge shows a prominent me- da Iberia e transforma9oes globais” (Funda9ao para a Cien- dian angle that corresponds to a vertical edge in the lingual cia e para a Tecnologia). Projecto “POCTI / 36531 / PAL/ face. The broad, lowerborder of the labial is ridge slightly 2000 - Studies on Portuguese Paleontology (Post- close concave by the marginal angles. The root comprises 3 Paleozoic)”. Funda9ao para a Ciencia e a Tecnologia/ Min- blades 2 separated by deep grooves. isterio da Ciencia e das Universidades. Observation of
Pliocene fossil selachians from the Elche region, Spain was
Discussion - As far as we can the studied judge, myliobatid possible owing to the courtesy of Mr. Jose Manuel Marin teeth different from those of the with are quite genera ex- Ferrer- Grupo Cultural Paleontologico de Elche. We thank tant representatives. A more accurate identificationdoes the reviewers for their usefulremarks. not seem possible.
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