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Humblet, M. and Iryu, Y. 2014: Pleistocene coral assemblages on Irabu-jima,

South Ryukyu Islands, Japan. Paleontological Research,

doi: 10.2517/2014PR020.

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doi:10.2517/2017PR025 Fossil herpetocetine baleen whales (Cetacea, Mysticeti, Cetotheriidae) from the lower

Pliocene Horokaoshirarika Formation at Numata, Hokkaido, northern Japan

YOSHIHIRO TANAKA1, 2, 3, HITOSHI FURUSAWA4 AND LAWRENCE G.

BARNES5

1 Osaka Museum of Natural History, Nagai Park 1-23, Higashi-Sumiyoshi-ku, Osaka,

546-0034, Japan (e-mail: tanaka@mus-nh.city.osaka.jp)

2 Numata Fossil Museum, 2-7-49, Minami 1, Numata town, Hokkaido 078-2225

Japan

3Hokkaido University Museum, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-

0810 Japan

4Sapporo Museum Activity Center, 5-15-1-6, Hiragishi, Toyohira-ku, Sapporo,

Hokkaido 060-0001, Japan.

5Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los

Angeles, California 90007, U.S.A.

Abstract. Two mandibles of fossil mysticetes from the early Pliocene, upper part

of the Horokaoshirarika Formation at Numata Town, Hokkaido, Japan, belong

to the archaic, extinct cetotheriid baleen whale, Herpetocetinae, gen. et sp. indet.

by having an elongated angular process projecting posteriorly beyond the

mandibular condyle. The new materials of the Herpetocetinae represent the

northernmost occurrence in the North Pacific.

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Key words: baleen whale, fossil, geographic range, Herpetocetinae, systematics

Introduction

The baleen whale family Cetotheriidae has varied in both its context and its content.

Early accounts, for example, by Kellogg (1928) and Simpson (1945) included

numerous species within this family that are now considered to belong to other

mysticete clades. Today, Cetotheriidae are more strictly defined as the monophyletic

clade including Cetotherium rathkii Brandt, 1843, as first recovered in the

phylogenetic analysis of Bouetel and de Muizon (2006).

Steeman (2007) recognized the subfamily Herpetocetinae, which was subsequently

defined by Whitmore and Barnes (2008) to include Herpetocetus and Nannocetus

based on their distinctive cranio-mandibular articulation. Recently, Bisconti (2014)

described a new mysticete, Herentalia nigra, referred to Herpetocetinae. However, H.

nigra has a much larger skull than the known herpetocetines, and it forms a clade with

Herpetocetus sp. (NMNS-PV 19540). The later analysis of Marx and Fordyce (2016)

put Herentalia in the Cetotheriidae, but not in the Herpetocetinae. Thus, here,

Herpetocetinae includes only Herpetocetus and Nannocetus.

There is an abundant record of herpetocetine material from Japan (Oishi and

Hasegawa, 1995), but little has been formally described. Inside Japan, herpetocetines

are known mostly from eastern Honshu. By contrast, records from northernmost

Japan, specifically, the island of Hokkaido are rare. A single tympanic bulla was

previously reported as having similarities with Herpetocetus sp. from Chiba and

Sendai, but only diagnosed to "Cetotheriidae, genus and species indeterminate”

(Shinohara and Tanaka, 2007). Here, we report two mandibles from exposures along

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the Uryu and Horonitachibetsu Rivers at Numata Town (Figure 1), Hokkaido, which

are well known for their Pliocene marine fossils, including mysticetes (e.g. Ichishima,

2005; Kimura et al., 1987; Tanaka, 2016a). The two mandibles are referable to

Herpetocetinae, and represent the northernmost record of the subfamily in the North

Pacific.

Institutional abbreviations.—AMP = Ashoro Museum of Paleontology, Ashoro

Town, Hokkaido, Japan; IRSNB = Institut Royal des Sciences Naturelles de Belgique,

Brussels, Belgium; MNHN = Muséum National d’Histoire Naturelle, Paris, France;

NFL = Numata Fossil Museum, Numata Town, Hokkaido, Japan; NMNH-P =

Academian V. A. Topachevsky Paleontological Museum of the National Museum of

Natural History of the National Academy of Sciences of The Ukraine; NMNS =

National Museum of Nature and Science, Tsukuba, Japan; SDNHM = San Diego

Natural History Museum, San Diego, California, USA; UCMP = University of

California Museum of Paleontology, Berkeley, California, USA; VMW = Sierra

College Natural History Museum, Rocklin, California, USA.

Systematic paleontology

Class Mammalia Linnaeus, 1758

Order Cetacea Brisson, 1762

Unranked taxon Neoceti Fordyce and de Muizon, 2001

Suborder Mysticeti Gray, 1864

Family Cetotheriidae Brandt, 1872

Subfamily Herpetocetinae Steeman, 2007

Herpetocetinae, gen. et sp. indet.

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Figures 2–5

Remarks.—The two mandibles reported herein, NFL 14 and 1025 belong to the

subfamily Herpetocetinae because of their far posteriorly projected angular process,

which exceeds that of all other cetotheriids in length (see Whitmore and Barnes,

2008). This mandibular morphology is consistent with that of species that have

previously been referred to Herpetocetus. However the specimens from Numata have

angular processes that differ from those of any other previously named species.

Geologic age and stratigraphy.—The two mandibles (NFL 14 and NFL 1025) were

collected from the upper part of the marine Horokaoshirarika Formation (Furusawa et

al., 1993) at Numata, Hokkaido, which is early Pliocene in age (Figure 1).

At the localities, a sedimentary sequence is exposed, comprising approximately 200

m of the upper part and 500 m of the lower part of the Horokaoshirarika Formation

(Watanabe and Yoshida, 1995). The boundary between the two is indicated by a thin

tuff layer (Kobayashi et al., 1969).

The marine Ichinosawa Formation and Bibaushi Formation both overlie the

Horokaoshirarika Formation, and are exposed along the lower parts of the

Horonitachibetsu River (Kobayashi et al., 1969), but not along the bed of the Uryu

River. The older, Miocene, marine Horoshin Formation underlies the

Horokaoshirarika Formation, and is exposed 2 km upstream from the locality of NFL

1025, and 3 km upstream from the locality of NFL 14.

The tuff separating the lower and upper parts of the Horokaoshirarika Formation has

been dated to approximately 4.5 Ma±0.7 Ma (Wada et al., 1986). The diatom

biostratigraphy suggests the age of the upper part of the Horokaoshirarika Formation

to be approximately 4.5 Ma to 3.9 or 3.5 Ma, and corresponds to the Thalassiosira

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oestrupii Zone (Nakashima and Watanabe, 2000). Therefore, the age of the upper part

of the Horokaoshirarika Formation corresponds to approximately 4.5 Ma to 3.5 Ma,

or the early Pliocene.

In addition to the fossil mysticetes described here, the upper part of the

Horokaoshirarika Formation has also produced other marine vertebrates, including the

phocoenid Numataphocoena yamashitai Ichishima and Kimura, 2000 (same locality

as NFL 1025; see also Tanaka, 2016b; Tanaka and Ichishima, 2016) and fossil

pinnipeds (Yamashita and Kimura, 1990; Kohno et al., 1995).

Referred specimen NFL 14.—An incomplete right mandible (Figures 2, 3, 6C, Table

1), collected by Toshitsugu Maeda on 17 August 1988, and prepared by Shigeru

Yamashita. The locality is in the bed of the Uryu River, in the 2nd Takaho District of

Numata Town (Figure 1).

Only the posterior portion of NFL 14 is preserved. The remaining part of the body is

slightly curved laterally and dorsally, and contains five anteriorly-opening mental

foramina, which are 3–4 mm in diameter. Anteriorly, the cross section of the body

becomes both higher and thinner. At the point of fracture, the mandibular canal is

round in cross section and has a diameter of 8.5 mm.

The ramus consists of the broken base of what appears to have been a relatively low

coronoid process. The mandibular foramen is deeply excavated, with a robust lower

border and a rounded anterior rim; it measures 33.0 mm in height and 22.5 mm in

length. The articular surface of the mandibular condyle faces posterodorsally. The

posterior end of the angular process extends far posterior to the articular surface of the

mandibular condyle. Where the angular process is broken off, it is nearly rectangular

in cross section (26.0+ mm wide, 20.0 mm high).

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Referred specimen NFL 1025.—A nearly complete right mandible (Figures 4, 5, 6D,

Table 2), found by Shigeru Yamashita on 15 June 1994, and collected by Shigeru

Yamashita, Takaoki Harada and Hitoshi Furusawa. The locality is in the bed of the

Horonitachibetsu River, in the 3rd Hokuryu District of Numata Town (Figure 1).

The posterior portion of the body of NFL 1025 is more clearly bowed laterally than

NFL 14. In lateral view, the body is somewhat arched dorsally and markedly expands

in height anteriorly. There are at least three anteriorly opening mental foramina, each

of which is approximately 2.5 mm in diameter. The anterior end of the body is

somewhat triangular in cross section, with the ventral border being relatively thin. The

symphyseal groove is relatively shallow.

The mandibular foramen (Figures 4 and 5E, H) is deeply excavated, but otherwise

poorly preserved. The articular surface of the mandibular condyle is elongate and

oriented posterodorsally. As in NFL 14, the subcondylar furrow is broad and poorly

defined. The angular process is nearly complete, elongate, and extends for

approximately 58.0 mm posterior to the articular surface of the mandibular condyle.

Dorsally, the robust apex of the angular process is connected to the mandibular

condyle by a relatively narrow subcondylar furrow. Medially, the angular process is

flat in the likely area of insertion of the medial pterygoid muscle.

Overall, the two mandibles are similar in size, as indicated by mandibular condyle

widths of 30.0 mm (NFL 14) and 33.0 mm (NFL 1025), respectively. However, NFL

1025 differs in having a more elongate mandibular condyle, a more robust angular

process and a thicker dorsal connecting ridge between the two (15.0 mm vs 8.0 mm).

Such differences may reflect specific, ontogenetic, sexual, or individual variation, but

other, more complete, specimens are required to elucidate this.

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Discussion

Comparisons with other herpetocetines

Of all described cetotheriids, the mandibles from Numata most closely resemble

herpetocetines. The only other possible contender, Piscobalaena nana, differs from

the present material in having a shorter angular process, a less depressed posterior

portion of the mandibular condyle, and a wider body with a blunter ventral and a

sharper dorsal margin (e.g. MNHN SAS 1618; Bouetel and de Muizon, 2006).

The relatively large size of the mandibles from Numata suggests that they likely

represent Herpetocetus, rather than the comparatively small Nannocetus. However,

Nannocetus is currently only known from fragmentary juvenile cranium lacking the

mandible, which makes comparisons with this taxon difficult. Better preserved

material of an ontogenetically more mature individual is needed to clarify the

morphology and relationships of Nannocetus, as well as its putative status as a genus

separate from Herpetocetus.

Within Herpetocetus, the mandibles from Numata differ from H. scaldiensis

(IRSNB 14; see also Whitmore and Barnes, 2008; Figure. 1) in having a shorter but

also higher angular process. They resemble H. bramblei in having a dorsally arched

body, but also differ from this species in being more elongated, more slender, and in

having a somewhat more convex (dorsoventrally) medial border.

Finally, the specimens from Numata are both larger and more robust than the

holotype of H. morrowi (UCMP 129450), which furthermore might also be 2–3

million years younger (El Adli et al. 2014). A paratype of H. morrowi, SDNHM

35294, preserves only the anterior part, and its size and shape is very similar to NFL

1025. Another paratype, SDNHM 32138, shows a broken angular process, but the

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preserved base is more slender than that of NFL 1025.

Overview of cetotheriid records from Hokkaido

There are three previous reports of “cetotheriid” fossils from Hokkaido (Egashira

and Kimura, 1998; Amano and Little, 2005; Shinohara and S. Tanaka, 2007); however,

not all of these may be members of the Cetotheriidae as presently defined.

Egashira and Kimura (1998) reported “the first Cetotheriidae from Hokkaido”,

AMP 35 (Taiki specimen 1 in the study) from a middle Miocene deposit. This

specimen, which was also briefly mentioned by Kimura and Ozawa (2002), includes

the posterior portion of the skull, the right mandible, the right tympanic bulla (not

illustrated in the publication), and the atlas. The mandible has a relatively short

angular process, that terminates anterior to the articular surface of the mandibular

condyle, unlike in cetotheriids. Regarding the taxonomic history of the family

Cetotheriidae, the early accounts by Kellogg (1928) and Simpson (1945) included

numerous species within the family, which are now considered to belong to other

mysticete clades. AMP 35 is one of the case, and is not demonstrably a member of the

family Cetotheriidae sensu stricto.

In our opinion, AMP 35 is similar to the late early Miocene holotype of Isanacetus

laticephalus Kimura and Ozawa, 2002, from Mie Prefecture, Japan. The two

specimens share transversely narrow and anteroposteriorly elongated nasal bones, as

well as a deeply concave orbital margin of the supraorbital process of the frontal.

Isanacetus has been interpreted as a stem mysticete (Deméré et al., 2005), a stem

balaenopterid (Kimura and Ozawa, 2002), or a member of the clade Balaenopteridae

+ Cetotheriidae (Bisconti, 2008; Bisconti et al., 2013; Gol'din et al., 2014; Marx,

2015).

The second putative record of cetotheriids from Hokkaido consists of a skull

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fragment of a mysticete (NMNS-PV 20913) from the lower middle Miocene

Chikubetsu Formation exposed near Shosanbetsu Village. It was reported in

association with mollusk fossils and identified as belonging to the "cetothere group"

based on a personal communication with N. Kohno at NMNS (Amano and Little,

2005). More recently, open-access database at NMNS

(http://db.kahaku.go.jp/webmuseum_en/collect/search_rule.do;jsessionid=9177FE1F1

A1F69604E8EFF8C4D2A8D7A?class_name=col_c2_02) has re-identified the

specimen as a balaenomorph, instead of non-monophyletic “cetothere group.” The

skull fragment does not show clear Cetotheriidae features; thus we follow the

database identification.

The final report of a cetotheriid from Hokkaido is that of Shinohara and Tanaka

(2007), who identified a bulla, NFL 2162 as belonging to a cetotheriid. Regarding the

study, NFL 2162 is similar to Herpetocetus based on having an echelon, which was

mentioned by Oishi and Hasegawa (1995) as a diagnosis of the Herpetocetus.

Shinohara and Tanaka (2007) did not identify in genus level, because lack of

comparison with other cetotheriids. Here, we follow the authors’ identification, and

recognize that the specimen is the first cetotheriid sensu stricto record from Hokkaido,

but cannot identify as a Herpetocetus because the feature is also seen on a species of

the family Cetotheriidae, Piscobalaena sp. (see Fig. 33 of Bouetel and de Muizon,

2006), and probably be highly effected by ontogeny.

In the text of Shinohara and Tanaka (2007), the two mandibles (NFL 14 and 1025)

were mentioned possibilities as Herpetocetus sp. and Nannocetus sp. with personal

communication of H. Furusawa.

Paleobiogeographic patterns

Herpetocetinae appear to have been distributed throughout the temperate latitudes of

the Northern Hemisphere with records from both the eastern and western North

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Pacific, and the eastern and western North Atlantic. Together, these occurrences range

in age from the late Miocene through the Pliocene, and at least one species may have

persisted into the Pleistocene (Boessenecker, 2013b) (Figure 7, Table 2).

Whitmore and Barnes (2008) reviewed the typology and geologic provenance of

Herpetocetus scaldiensis Van Beneden, 1872, and assigned to the species additional

specimens, all of them from the same deposit in Belgium that yielded the lectotype

and the other specimens that were originally described by Van Beneden (1872, 1882).

The first report of the genus Herpetocetus in the fossil record of the western North

Atlantic was the description of Herpetocetus transatlanticus Whitmore and Barnes,

2008 from the early Pliocene of North Carolina, U.S.A. In the eastern North Pacific

basin, Herpetocetus occurs in the latest Miocene to earliest Pliocene parts of the

Capistrano Formation in southern California and from the approximately

contemporaneous Purisima Formation in central California (Barnes 1977;

Boessenecker 2013a; Whitmore and Barnes, 2008). The geochronologically youngest

named species is the late Pliocene Herpetocetus morrowi El Adli et al., 2014, from

the San Diego Formation at San Diego, California, U.S.A (El Adli et al., 2014).

Records of Herpetocetus and of Herpetocetus-like mysticetes are not uncommon in

Japan (Hatai et al., 1963; Oishi and Hasegawa, 1995; Shinohara and S. Tanaka, 2007;

the present study). The early Pliocene Herpetocetus bullae recorded from Choshi in

Chiba Prefecture by Oishi and Hasegawa (1995) are the southern-most records of

Herpetocetus in Japan. By contrast, the mandibles from Numata Town, Hokkaido, are

the northern-most records of Herpetocetinae in the North Pacific Ocean.

Conclusions

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Two mandibles from the early Pliocene Horokaoshirarika Formation at Numata,

Hokkaido, Japan, represent the northernmost record of the fossil mysticete subfamily

Herpetocetinae in the North Pacific. These mandibles cannot currently be assigned to

this genus owing to the uncertainty surrounding the status of Nannocetus. The

mandibles in particular appear to differ from all described species of Herpetocetus,

and may indicate a further increase in herpetocetine taxonomic diversity.

Acknowledgements

We thank Toshitsugu Maeda (Sapporo City, Fujino Jr. High School), Takaoki

Harada (Numata Jr. High School) for collecting and preparing the specimens. YT

thanks Satoshi Shinohara (Numata Fossil Museum) for guiding him to fossil localities

in Numata Town; and Hiroshi Sawamura and Tatsuro Ando (Ashoro Museum of

Paleontology) for access to AMP 35. We also thank Felix G. Marx (Royal Belgian

Institute of Natural Sciences, Belgium, and Monash University, Australia), Cheng-

Hsiu Tsai (National Museum of Nature and Science, Japan) and Toshiyuki Kimura

(Gunma Museum of Natural History) for providing constructive reviews of the

manuscript. YT thanks R. Ewan Fordyce (University of Otago) for his comments to

this manuscript and encouragement on this project, Felix G. Marx for discussions on

cetotheriid systematics and morphology, Robert Boessenecker (College of

Charleston) for constructive comments on an earlier draft of this manuscript, Naoki

Kohno (National Museum of Nature and Science, Japan) for providing the

opportunity to examine specimens (NMNS-PV 19540), Nicholas D. Pyenson and

David J. Bohaska (United States National Museum of Natural History), Jun Nemoto

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(Tohoku Univesity Museum), Masaya Oishi and Takafumi Mochiduki (Iwate

Prefecture Museum), and Tadasu Yamada and Yuko Tajima (National Museum of

Nature and Science, Japan) for providing access to comparative specimens. YT thanks

Olivier Lambert (Institut Royal des Sciences Naturelles de Belgique) for providing

references. HF and LGB benefitted from support from the Hokkaido University of

Education and the Natural History Museum of Los Angeles County and its foundation

for travel in Japan and the United States. We thank Masaichi Kimura (Hokkaido

University of Education, Numata Fossil Museum) for his encouragement to this

project.

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List of figures and tables

Figure 1. Maps showing the localities of herpetocetine cetotheriid mysticetes from

Numata Town, Hokkaido, Japan, reported in this study. A, locality of NFL 1025 on

the bed of the Horokaoshirarika River; B, locality of NFL 14 on the bed of the Uryu

River. C, stratigraphic column at the localities, which is modified from Tanaka and

Ichishima (2016). The map of Japan and Numata Town are modified from Tanaka and

Kohno (2015) and Tanaka and Ichishima (2016) respectively.

Figure 2. Herpetocetinae, gen. et sp. indet., incomplete right mandible, NFL 14. A,

dorsal view; B, medial view; C, ventral view; D, lateral view; E, posterior view; F,

anterior view. Dashed lines indicate missing parts based on published specimens of

Herpetocetus and NFL 1025, described herein.

Figure 3. Herpetocetinae, gen. et sp. indet., incomplete right mandible with structures

labeled, NFL 14. A, dorsal view; B, medial view; C, ventral view with cross section;

D, lateral view; E, posterior view; F, anterior view showing cross section at transverse

break. Dashed lines indicate missing parts based on published specimens of

Herpetocetus and on NFL 1025, described herein.

Figure 4. Herpetocetinae, gen. et sp. indet., nearly complete right mandible, NFL

1025. A, dorsal view; B, medial view; C, lateral view; D–H, enlarged views of

separated posterior part; D, lateral view; E, posterior view; F, dorsal view; G, ventral

view; H, medial view.

Figure 5. Herpetocetinae, gen. et sp. indet., nearly complete right mandible with

Accepted manuscript

21

structures labeled, NFL 1025. A, dorsal view; B, medial view; C, lateral view;.D–H,

enlarged views of separated posterior part; D, lateral view; E, posterior view; F, dorsal

view; G, ventral view; H, medial view. Dashed lines indicate missing parts based on

other published specimens of Herpetocetus and on NFL 14, described herein.

Figure 6. Cetotheriidae, posterior parts of mandibles of various species in lateral view.

A, Cetotherium riabinini (holotype, NMNH-P 668/1) redrawn from Gol’din et al.,

(2014); B, Piscobalaena nana (MNHN SAS 1618) redrawn from Bouetel and de

Muizon (2006); C, Herpetocetinae gen. et sp. indet. NFL 14; D, Herpetocetinae gen.

et sp. indet. NFL 1025; E, Herpetocetus morrowi (holotype, UCMP 129450) redrawn

from El Adli et al., (2014); F, Herpetocetus scaldiensis (lectotype, IRSNB 14)

redrawn and reversed from Van Beneden (1882); G, Herpetocetus bramblei (UCMP

219079) redrawn and reversed from Boessenecker (2013a); H, Herpetocetus sp.

(NMNS-PV 19540) redrawn and reversed from Bouetel and de Muizon (2006).

Figure 7. Paleogeographic distribution of the cetotheriid subfamily Herpetocetinae.

Table 1. Herpetocetinae, gen. et sp. indet., measurements in mm of mandibles, NFL

14 and NFL 1025, following the methods of Tsai and Fordyce (2015). Measurements

are rounded to the nearest 0.5 mm. Parameters are measured in either the transverse or

the dorso-ventral dimensions.

Table 2. List of reported Herpetocetinae.

Mandibles NFL 14 NFL 1025

Length of mandible, as preserved in straight line

490.0+ 1250.0+

Height of mandible, from coronoid process to ventral margin

54.5+ 80.0

Maximum preserved height of mandible

54.5 69.0

Maximum preserved width of mandible

41.0 41.0

Height of body at just anterior to coronoid process 42.0 -Width of body at just anterior to coronoid process

32.0-

Identification Age Formations Localities Materials Reference

Herpetocetus sp.early to middle Pleistocene

Falor Fm. California, USA

Skull and periotic (VMW-65)

Boessenecker (2013b)

Herpetocetus morrowi (Type)

late Pliocene San Diego Fm.

California, USA

Skull, periotics, bullae, mandible, vertebrae, ribs and humerus (UCMP 129450) and 42 pratypes

El Adli et al. (2014)

Herpetocetinae gen. et sp. indet.

early PlioceneHorokaoshirarika Fm.

Hokkaido, Japan

Mandibles (NFL 14, 1025)

Shinohara and Tanaka (2007) and This study

Herpetocetus sp. early PlioceneTatsunokuchi Fm.

Miyagi, Japan

Skeleton (NSMT-PV 19540)

Oishi et al. (1985)

Herpetocetus sp. early PlioceneTatsunokuchi Fm.

Miyagi, Japan

7 bullaeOishi and Hasegawa (1995)

Herpetocetus sp. early Pliocene Yushima Fm.Iwate, Japan

3 bullaeOishi and Hasegawa (1995)

aff. Herpetocetus sp. early Pliocene Yushima Fm.Iwate, Japan

1 bullaOishi and Hasegawa (1995)

cf. Herpetocetus sp. (Group I in the publication)

early Pliocene Na-arai Fm.Chiba, Japan

5 bullaeOishi and Hasegawa (1995)

Herpetocetus bramblei (Type)

early Pliocene Purisima Fm. California, USA

Left half skull, left periotic and right mandible (UCMP 82465)

Whitmore and Barnes (2008)

Herpetocetus bramblei early Pliocene Purisima Fm. California, USA

Mandible (UCMP219079)

Boessenecker (2013a)

Herpetocetus sp. early Pliocene Purisima Fm. California, USA

Squamosal, periotics and bullae (7 UCMP specimens were referred)

Boessenecker (2013a)

Herpetocetus transatlanticus (Type)

early Pliocene Yorktown Fm.North Carolina, USA

Partial skull, left periotic and bulla (USNM 182962) and 11 paratypes

Whitmore and Barnes (2008)

Herpetocetus sp. early Pliocene Yorktown Fm.North Carolina, USA

Periotic (USNM 299652)

Geisler and Luo (1996)

Nannocetus eremus late Miocene Calvert Fm.Marryland, USA

Skull, bullae and periotics (UCMP 26502)

Kellogg (1929)

Herpetocetinae, gen. et sp. indeterminate

late MioceneSanta Margarita Sandstone

California, USA

Mandible (UCMP 85431)

Boessenecker (2011)

Herpetocetus scaldiensis (Type)

? ?Antwerp, Belgium

Mandible (IRSNB 14) Van Beneden (1872), Abel (1938)

Herpetocetus scaldiensis (Referred)

? ?Antwerp, Belgium

Left squamosal (IRSNB 405), partial skull and right periotic, bulla and stapes (USNM 336361)

Whitmore and Barnes (2008)

Herpetocetus scaldiensis (Referred, but not illustrated and described)

Pleistocene Red CragEngland, UK

Bulla (at Museum of Practical Geology) and unknown element (No. 2816 at the Museum of the College of Surgeons) Lydekker (1887)

aff. Herpetocetus sp. middle MioceneRosarito Beach Fm.

Baja California, Mexco ? Barnes (1998)