Submitted : September 26 th , 2020 – Accepted : June 4th , 202 1 – Posted online : June 16 nd , 202 1
To link and cite this article:
doi: 10.5710/AMGH.04.06.2021.3403
1 NEW RECORD OF A PHOCID (MAMMALIA, CARNIVORA, PHOCIDAE) IN
2 THE LATE MIOCENE OF PATAGONIA, ARGENTINA
3 NUEVO REGISTRO DE UN FÓCIDO (MAMMALIA, CARNIVORA, PHOCIDAE) EN
4 EL MIOCENO TARDÍO DE PATAGONIA, ARGENTINA
5
6 SEBASTIÁN ECHARRI,*,1 DAMIÁN E. PEREZ,2 MARCELO MIÑANA,1 AND
7 SERGIO O. LUCERO,1
8 1 Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" – CONICET.
9 Av. Ángel Gallardo 470, C1405DJR, Buenos Aires, Argentina.
10 [email protected]; [email protected];
12 2 Instituto Patagónico de Geología y Paleontología (IPGP CCT CONICET-CENPAT), Bvd.
13 Brown 2915, U9120CD, Puerto Madryn, Chubut, Argentina. [email protected]
14
15 16 págs. (text+references); 2 figs.
16
17 Running header: ECHARRI ET AL.: NEW PHOCID FROM PATAGONIA
18 Short description: New fossil record of a phocid from Puerto Madryn Formation, the first
19 skull remains for the group in Patagonia.
20
21 Corresponding author: Sebastián Echarri, [email protected]
1
22
23 Keywords. Chubut. Kawas. Neogene. Pinnipedia. Properichtychus. Puerto Madryn
24 Formation. South Atlantic.
25 Palabras clave. Chubut. Kawas. Neógeno. Pinnipedia. Properichtychus. Formación Puerto
26 Madryn. Atlántico Sur.
20
27
28 TRUE SEALS (family Phocidae) include 19 living species grouped in two living subfamilies:
29 Monachinae Gray, 1869 and Phocinae Gray, 1821 (e.g., King, 1964; Bastida et al., 2007).
30 Monophyly of the Phocidae is supported by morphological and molecular evidence (Davis
31 et al., 2004; Higdon et al., 2007; Amson & Muizon, 2014; Berta et al., 2018). A third
32 subfamily, the Devinophocinae, includes only one genus with two fossil species:
33 Devinophoca claytoni and D. emryi (Koretsky & Holec, 2002; Koretsky & Rahmat, 2015;
34 Rahmat & Koretsky, 2018). The subfamily Monachinae presents three well-differenced
35 clades: the tribes Monachini (monk seals), Miroungini (elephant seals), and Lobodontini
36 (leopard seals and others); while the subfamily Phocinae includes: the tribes Erignathini
37 (bearded seals), Cystophorini (hooded seals), and Phocini (common seals) (Muizon, 1981;
38 Koretsky, 2001; Davis et al., 2004; Higdon et al., 2007; Fulton & Strobeck, 2010; Scheel et
39 al., 2014; Berta et al., 2018). This classification is primarily based on living taxa, but other
40 authors proposed different arrangements. For example, Koretsky & Rahmat (2013)
41 suggested a fourth subfamily, the Cystophorinae, including some former members of the
42 Monachinae.
43 Based on current distributions, species of Phocinae are commonly considered
44 Boreal seals (King, 1964; Dewaele et al., 2018a,b). However, during the Neogene, the
45 Phocinae has at least one record in the Southern Hemisphere (Cozzuol, 2001), and the
46 species of the Monachinae seals were present in the Northern and Southern Hemispheres
47 (Muizon, 1981; Berta et al., 2015; Govender, 2015; Dewaele et al., 2018b).
48 In the Southern Hemisphere, fossil phocids are restricted to a few scattered
49 localities in Chile, Perú, Argentina, South Africa, Australia, and New Zealand (Hendey & 20
50 Repenning, 1972; Muizon & Hendey, 1980; Muizon, 1981; Cozzuol, 2001; Walsh & Naish,
51 2002; Fitzgerald, 2005; Valenzuela-Toro et al., 2013, 2015; Berta et al., 2018; Rule et al.,
52 2019, 2020). On the South Eastern Atlantic coast, fossils of seals are restricted to few
53 localities from the Miocene and Pleistocene of Argentina (Muizon & Bond, 1982; Cozzuol,
54 1996, 2001; Soibelzon & Bond, 2013).
55 Two phocid species are known for the Miocene of Argentina, Properiptychus
56 argentinus (Ameghino, 1893) and Kawas benegasorum Cozzuol, 2001. The holotype of P.
57 argentinus is a right maxilla from the Paraná Formation, Entre Ríos Province, originally
58 described by Ameghino (1893) as a condylarth, but posteriorly assigned to Monachinae
59 (Muizon and Bond,1982; see also Rule et al., 2020a,b). Additional specimens include teeth
60 and isolated postcranial elements (Muizon & Bond, 1982; Soibelzon & Bond, 2013).
61 Kawas benegasorum is only known by the holotype, a partially articulated skeleton from
62 the Puerto Madryn Formation, but no parts of the skull are known for this species, except
63 for three isolated teeth (Cozzuol, 2001). This taxon was described initially as a Phocinae
64 (Cozzuol, 2001) but this phylogenetic interpretation was later discussed (Koretsky and
65 Domning, 2014). Recent phylogenetic analyses placed Kawas as a stem Phocinae (Berta et
66 al., 2018; Dewaele et al., 2018a) or related to Devinophoca Koretsky & Holec, 2002 (Rule
67 et al., 2020b).
68 In this contribution, we describe a dentary fragment attributed to a phocid from the
69 Puerto Madryn Formation, late Miocene of Valdés Peninsula, Chubut, Argentina (Figs. 1–
70 2). Despite its fragmentary nature, the scarce fossil record of Pinnipedia in the South
71 Eastern Atlantic coast makes the present record noteworthy. This dentary is the second
72 report of a phocid in the Miocene of Patagonia. 20
73 Institutional Abbreviations. MACN, Museo Argentino de Ciencias Naturales “Bernardino
74 Rivadavia”, Ciudad Autónoma de Buenos Aires, Argentina (A, Colección Ameghino, Pv,
75 Colección Paleontología de Vertebrados, MA, Colección Mastozoología); MEF, Museo
76 Paleontológico “Egidio Feruglio”, Trelew, Chubut, Argentina; MASP, Museo de Ciencias
77 Naturales y Antropológicas “Prof. Antonio Serrano” (ex Museo de Entre Ríos), Paraná,
78 Entre Ríos, Argentina.
79 Specimens used for comparisons. MACN-A 11593 (holotype of Properiptychus
80 argentinus); MACN-Pv 3538 (Properiptychus argentinus); MASP 685 (Phocidae indet.);
81 MEF-PV 601 (Kawas benegasorum); MACN-Ma 13.26 (Mirounga leonina); MACN-Ma
82 20435 (Hydrurga leptonyx); MACN-Ma 20628 (Leptonychotes weddellii); MACN-Ma
83 19.20 (Lobodon carcinophaga); MACN-Ma 48.259 (Ommatophoca rossii).
84
85 SYSTEMATIC PALEONTOLOGY
86 Order CARNIVORA Bowdich, 1821
87 Suborder PINNIPEDIA Illiger, 1811
88 Superfamily PHOCOIDEA Gray, 1825
89 Family PHOCIDAE Gray, 1821
90 Phocidae gen. et sp. indet.
91 Fig. 2.1–2.3
92 Referred material. MACN-Pv 20064, a fragment of an edentulous right dentary (Fig. 2.1–
2.3). 93 2.3).
94 Geographic occurrence. MACN-Pv 20064 was collected from the cliffs southeast of
95 Puerto Pirámides, Valdés Peninsula, Patagonia, Argentina. 20
96 Stratigraphic occurrence. MACN-Pv 20064 comes from the upper levels of the Puerto
97 Madryn Formation (Fig. 1). This unit is formed by 150 meters of intercalation of coquinas,
98 tuffs, limestones, sandstones, and heterolithic sandstones. A regressive phase is recognized
99 towards the top of the sequence (del Río et al., 2001). A late Miocene age was proposed
100 based on microfossils (Malumián & Masiuk, 1973; Masiuk et al., 1976; Malumián, 1978)
101 and supported by vertebrates (Dozo et al., 2010) and mollusks (del Río, 1990). Also, early
102 late Miocene radiometric ages were determined close to the top (10 ± 0.3 Ma; Scasso et al.,
103 2001) or at the top (9.41 Ma; Zinsmeister et al., 1981) of the unit. Sedimentation of the
104 Puerto Madryn Formation corresponds to a marine transgression informally known as the
105 “Entrerriense” Transgression (see Cuitiño et al., 2017 for stratigraphic description and
106 palaeoenvironmental reconstruction).
107 The Puerto Pirámides stratigraphic section of the Puerto Madryn Formation exposes
108 northeast of the Golfo Nuevo and 2 km east from the homonym locality. It is formed by 50
109 meters of sandstones, tuffaceous sandstones, and limestones, with cross-bedded
110 stratification and ondulites. These deposits correspond to a closed marine environment
111 dominated by tidal regimes in normal marine conditions (del Río et al., 2001). Fossil
112 vertebrates remains are well-preserved and usually disarticulated, and they are mainly
113 cetacean fragments, such as balaenids, neobalaenines, balaenopterids, and ziphiids (Cuitiño
114 et al. 2017). Fossil invertebrates include significant accumulations of the echinoid
115 Monophoraster darwini (Desor, 1847), abundant oysters, the pectinid ‘Aequipecten’
116 paranensis (d’Orbigny, 1842), and the brachiopod Pachymagas piramidesia (Ihering,
117 1903). The horizon where the Patagonian Phocinae K. benegasorum (MEF-Pv 601, Punta
118 San Román, north of the Valdés Peninsula) was collected (Cozzuol, 2001) correlates with 20
119 the level where MACN-Pv 20064 was found.
120 Description. MACN-Pv 20064 is an incomplete right dentary (Fig. 2.1–2.3), preserving the
121 medial portion of the body, with the alveoli for p3, p4, and m1. The body is low and
122 narrow, and it widens anteriorly. The mandibular canal is visible in anterior and posterior
123 views. The lingual and labial surfaces on the dentary are smooth. The symphysis and
124 masseteric fossa are not preserved (Fig. 2.1–2.3).
125 In occlusal view (Fig. 2.1), the margins of the dentary are sub-parallel. MACN-Pv
126 20064 has six well-defined alveoli corresponding to three birradiculated postcanine teeth
127 (p3, p4, and m1), with a rounded outline for alveoli of p3 and p4, and slightly oval for m1,
128 which is longer than wide. Alveoli are placed in a straight line and are nearly similar in
129 size. In labial view (Fig. 2.2), MACN-Pv 20064 presents a smooth surface and a concave
130 area at the level of p4, where the texture of the bone becomes slightly porous. There are
131 two mental foramina, opening in a common depression, located ventral to the position of
132 the interalveolar septum of p3 (Fig. 2.2). This position is almost identical to that of the
133 posteriormost mental foramina of Piscophoca sp. (Walsh & Naish, 2002) and a Phocidae
134 indet. of the Pliocene of Australia (Fitzgerald, 2005). Measurements are provided in Table
1. 135 1.
136 The concavity observed at the level of the p4 in labial and occlusal views could be
137 consistent with a pathology. The alveoli of p4 are damaged, but they remain open.
138
139
140 DISCUSSION
141 Taxonomical assignment of MACN-Pv 20064 20
142 MACN-Pv 20064 does not include elements preserving synapomorphies of suprageneric
143 pinniped taxa (see Berta, 1991; Berta & Wyss, 1994; Fitzgerald, 2005). MACN-Pv 20064 is
144 referred to the family Phocidae based on its morphology (e.g., alveoli corresponding to
145 large and bulbous birradiculate teeth, straight horizontal ramus with subparallel margins)
146 and measurements more similar to the dentaries of phocid seals than other pinnipeds
147 (families Odobenidae and Otariidae) (Fitzgerald, 2005). Also, postcanine teeth in the South
148 American otariids Arctocephalus and Otaria are unirradiculated. In MACN-Pv 20064 as in
149 birradiculate Phocidae, the alveolar walls between consecutive postcanine teeth are wider
150 than those observed between the anterior and posterior alveoli of a single birradiculate
151 teeth. In contrast, the alveoli of unirradiculate teeth in phocid species tend to be more
152 rounded and larger than the alveoli of birradiculate teeth. In otariids, the distance between
153 the alveoli is homogeneous, unlike what we observed in phocids. Consequently, we assign
154 MACN-Pv 20064 to the family Phocidae. Among phocids, the absence of an oblique tooth-
155 row differentiates MACN-Pv 20064 from the Monachinae subfamily, but because the
156 specimen lacks characters valuables for taxonomy (e.g., presence of mandibular mental
157 process or symphysis reaching the level of the alveolus of p2) (Koretsky & Domning,
158 2014) our determination is inconclusive. Because of the poor preservation of MACN-Pv
159 20064, we were unable to assign the specimen with certainty to the Monachinae or
160 Phocinae.
161
162 Comparisons with other fossil and living seals
163 MACN-Pv 20064 differs from the stem Phocidae genus Devinophoca Koretsky &
164 Holec, 2002 by having a higher dentary, broader and anteroposteriorly compressed alveoli 20
165 of m1 (which is single-rooted in Devinophoca claytoni Koretsky & Holec, 2002), and
166 mental foramina placed in a more central position of the ramus height (more dorsal in D.
167 claytoni and more ventral in D. emryi Koretsky & Rahmat, 2015) (Rahmat & Koretsky,
168 2018). MACN-Pv 20064 differs from the basal Phocinae Leptophoca True, 1906 by having
169 a less swollen and more robust body. Among fossil and living crown Phocidae seals,
170 MACN-Pv 20064 differs from the Phocinae seals of the genus Cystophora Nilsson. 1820,
171 by their less strong condition, with alveoli of p4 and m1 similar in size and alveoli of m1
172 with oval outline (Koretsky & Rahmat, 2013; Rahmat & Koretsky, 2018). MACN-Pv
173 20064 differs from Phoca largha Pallas, 1811 and P. vitulina Linnaeus, 1758 because they
174 have rounded molar alveoli, and from Halichoerus Nilsson, 1820 by their larger alveoli.
175 MACN-Pv 20064 differs from the genera Praepusa Kretzoi, 1941 and Cryptophoca
176 Koretsky & Ray, 1994 because the alveoli of p4 are not smaller than m1. MACN-Pv 20064
177 does not belong to a species of the extant genera of living Lobodontini or the genus
178 Mirounga Gray, 1827 (tribe Miroungini), because of its smaller size, lower height and less
179 strong condition. MACN-Pv 200064 shares with the fossil Lobodontini Hadrokirus Amson
180 & Muizon, 2014 a dentary body that widens anteriorly, but in the latter, the dentary is
181 higher and more robust, and tooth row is oblique. MACN-Pv 20064 differs from the
182 monachines Monachus Fleming, 1822, Pliophoca Tavani, 1941, Pontophoca Kretzoi, 1941,
183 and Afrophoca Koretsky & Domning, 2014 because it has a more slender dentary, with
184 postcanine alveoli placed in a straight line instead of an oblique line and the alveoli of p4
185 equal in size to p3. MACN-Pv 20064 is closer in morphology to the Pliocene monachinaes
186 Acrophoca longirostris Muizon, 1981 and Piscophoca capensis Muizon, 1981 from Peru,
187 and Homiphoca capensis Hendey & Repenning, 1972 from South Africa. However, 20
188 MACN-Pv 20064 is more robust than Acrophoca and less robust than Piscophoca, while
189 Homiphoca has the alveoli of p4 smaller than m1. A generic determination of MACN-Pv
190 20064 is impossible considering its poor state of preservation.
191
192 Comparisons with other Miocene seals of Argentina
193 We were unable to compare MACN-Pv 20064 with the holotype of Kawas
194 benegasorum, the only phocid known from the Puerto Madryn Formation, because this
195 lacks skull elements other than isolated teeth. In K. benegasorum teeth are double-rooted
196 and similar to Acrophoca, Piscophoca, and Homiphoca, whose roots match with the alveoli
197 of MACN-Pv 20064. The eventual assignment of MACN-Pv 20064 to K. benegasorum can
198 not be ruled out. Properiptychus argentinus (Fig. 2.4–2.6), the second phocid from
199 Argentina, recovered from the Paraná Formation differs from MACN-Pv 20064 by having a
200 dentary more robust, slightly higher, more labio-lingually expanded towards the anterior
201 end, and slightly more convex and with a roughly lateral surface. We were unable to
202 identify intraspecific or ontogenetic variation. We consider MACN-Pv 200064 as Phocidae
203 indet.
204 We also suggest that the postcranial elements (humerus, radius, and acetabular
205 region of pelvic girdle) that were assigned to Properiptychus argentinus by Muizon &
206 Bond (1982) and Soibelzon & Bond (2013) should be considered by caution, since the
207 holotype does not preserve comparable elements. It could not be ruled out that these
208 elements belong to another species of phocids. Also, Muizon & Bond (1982) assign the
209 specimen MASP 685 as a paratype of P. argentinus, but in the original description of the
210 species, Ameghino (1893) mentioned and described only the specimen MACN-A 11593. 20
211 The article 72.4 of the International Code of Zoological Nomenclature does not validate the
212 assignation of MASP 685 as paratype.
213
214 Paleobiogeographic interpretations
215 Many authors (e.g., Cozzuol, 2001; Arnason et al., 2006; Govender, 2015; Rule et al.,
216 2020b) interpreted a North Atlantic origin of the Phocidae, considering the late Oligocene
217 record of North America (Koretsky & Sanders, 1997) as the oldest for the group, followed
218 by several independent dispersal events between northern and southern hemispheres
219 (Cozzuol, 2001; Rule et al., 2020b). The presence of phocid seals in the Southern
220 Hemisphere has established early in the Neogene and later replaced by otariid seals
221 (Valenzuela-Toro et al., 2013). MACN-Pv 20064 is an example of the Miocene–Pliocene
222 radiation of the group in the South Hemisphere.
223 The morphology of MACN-Pv 20064 is consistent with Cozzuol’s hypothesis who
224 considered the presence of Phocidae (such as Phocinae seals) in the Miocene of South
225 America. New findings and studies of the known specimens has the potential to provide a
226 better understanding of the evolution of phocids in South America and their biogeographic
227 implications.
228 The oldest Phocidae remains in the Southern Hemisphere are from Beaumaris site in
229 Australia (late Miocene–early Miocene, Rule et al., 2020) and those from Argentina
230 (Kawas benegasorum, Properiptychus argentinus, and the material discussed in work). In
231 conclusion, MACN-Pv 20064 is the third Phocidae material for the South Western Atlantic
232 Ocean and one of the oldest for the family in the Southern Hemisphere.
233 ACKNOWLEDGMENTS 20
234 We want to thank the curators of MACN, Dr. Laura Chornogubsky and Dr. Martin Ezcurra
235 (Colección Nacional de Paleovertebrados), and Dr. Pablo Teta and Dr. Guillermo Cassini
236 (Colección Nacional de Mastozoología) for access to the collections under their care;
237 Marcos Becerra (MEF) for sending photographs of Kawas benegasorum, and Graciela
238 Ibargoyen (MASP) for sharing information about the specimens of Properiptychus
239 argentinus. Analía Forasiepi for suggestions with the grammar and observations. We also
240 thank Mario Cozzuol and two other anonymous reviewers for their valuable comments and
241 suggestions. This contribution is the first collaboration of Fufis (a group of researchers,
242 fellows and technicians formed in 2010 to analyze different questions of natural life and the
243 natural sciences during informal meetings in the halls of MACN).
244
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423 Figure captions.
424 Figure 1. Geographic and stratigraphic provenance of MACN-Pv 20064. Star indicates the
425 fossil locality and arrow indicates the level of origin.
426 Figure 2. 1–3. Dentary of MACN-Pv 20064. 4–6. Dentary of Properiptychus argentinus
427 MACN-Pv 3538. 1, occlusal view; 2, labial view; 3, lingual view; 4, oclusal view; 5, labial
428 view; 6, lingual view. Abbreviations, ac, mandibular canal; mf, mental foramina; p3 and
429 p4, inferior premolar 3 and 4 respectively; m1, inferior molar 1 Scale bar equals 10 mm.
20
TABLE 1. Measurements of MACN-Pv 200064 (in mm) Height between p3 and p4 22.5 (est.) Height under m1 23.20 (est.) Thickness of dentary at the level 12 of p3 Thickness of dentary at the level 10.29 of m1 Length of p3 11.22 Length of p4 12.17 Length of m1 13.48 p3 alveoli anterior / posterior Length 4.96 (inc.) / 4.19 Width 5.65 (inc.) / 5.13 p4 alveoli anterior / posterior Length 5.74 / 4.99 Width 4.6 / 4.92 m1 alveoli anterior / posterior Length 4.95 / 5.78 Width 4.23 / 3.77 “Inc.” refers to incomplete structures, and “est.” refers to an estimated measure.