Balaenoptera BERTAE N., n.
Balaenoptera bertae n. sp. (Figs 11-15) HOLOTYPE. — UCMP 219078, a partial skull lacking the premaxillae, maxillae, nasals, jugals, tympanic bullae, and bodies of the petrosal, excavated by R. W. Boessenecker, E. Johnson, T. Palladino, and M. Berrini from UCMP locality V99849 from August 12-15, 2005...
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2013
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| Online Access: | https://dx.doi.org/10.5281/zenodo.4818610 https://zenodo.org/record/4818610 |
| Summary: | Balaenoptera bertae n. sp. (Figs 11-15) HOLOTYPE. — UCMP 219078, a partial skull lacking the premaxillae, maxillae, nasals, jugals, tympanic bullae, and bodies of the petrosal, excavated by R. W. Boessenecker, E. Johnson, T. Palladino, and M. Berrini from UCMP locality V99849 from August 12-15, 2005. TENTATIVELY REFERRED SPECIMENS. — UCMP 131815, a partial juvenile cranium including the vertex, supraorbital processes of the frontals, palatines, and tips of the zygomatic processes collected in 1985 by a UCMP party from UCMP locality V85027; UCMP uncataloged, an isolated squamosal from UCMP locality V99868. ETYMOLOGY. — Honouring Dr Annalisa Berta (San Diego State University), for her many contributions to the study of fossil cetaceans and pinnipeds. DIAGNOSIS. — Balaenoptera bertae n. sp. is a small balaenopterid (estimated bizygomatic width of 61.4 cm), smaller in size than extant Balaenoptera acutorostrata Lacépède, 1804, characterized by: broadly triangular occipital shield that laterally overhangs the temporal fossa and exhibits a flattened apex, large occipital condyles, little to no parietal exposed dorsally at the transversely narrow vertex, squamosal with short, anteriorly directed zygomatic process, posteriorly elongate postglenoid process, prominent squamosal crease, frontal with rectangular supraorbital process with transversely oriented anterior margin, frontal that is abruptly depressed below the vertex and obliquely oriented so that this surface and anterior wing of parietal are visible in dorsal aspect, large petrosal fossa ( sensu Mead & Fordyce 2009), and a posterior process of the petrotympanic that is relatively short and inflated. STRATIGRAPHIC OCCURRENCE. — Uppermost part of the San Gregorio section of the Purisima Formation ( sensu Powell et al. 2007) that is bracketed below by an ash bed correlated with the 3.3-3.4 Ma Putah Tuff (Powell et al. 2007) and above by another ash bed correlated with the 2.5 ± 0.2 Ma Ishi Tuff. Ŋis indicates an age of 3.35-2.5 Ma, or Early to Late Pliocene (Piacenzian- Gelasian equivalent). TYPE LOCALITY. — UCMP locality V99849, Pliocene Purisima Formation. Detailed locality information available on request from UCMP or the author. DIFFERENTIAL DIAGNOSIS Balaenoptera bertae n. sp. is a member of the extant genus Balaenoptera and shares with all extant species of Balaenoptera a squamosal crease, relatively short and anteriorly oriented zygomatic processes, a bulge at the squamosal-parietal suture in the posterior temporal fossa, and a truncated apex of the occipital shield. Balaenoptera bertae n. sp. differs from: – Archaebalaenoptera castriarquati Bisconti, 2007, in having a broader occipital shield with a laterally sinuous margin that overhangs the temporal fossa and an anteriorly truncated apex, a transversely thinner vertex measuring only 10% of bizygomatic width (compared to 24% bizygomatic width in A.castriarquati ), short and blunt anteriorly directed zygomatic process that lack supramastoid crest that extends to the zygomatic apex, and having an anteroposteriorly shorter supraorbital process of the frontal; – “ Balaenoptera ” cortesi “var.” portisi , in having a squamosal crease, shorter and more anteriorly oriented zygomatic process that lacks a supramastoid crest that extends to the anteroventrally oriented zygomatic apex, transversely wide postglenoid process, an anteroposteriorly short supraorbital process with a transversely oriented anterior margin and laterally prominent antorbital process, a shallow sternomastoid fossa, and a large petrosal fossa; – “ Balaenoptera ” ryani Hanna & McLellan, 1924, in having a posteriorly broad occipital shield, little to no parietal exposed at the vertex, and an anteriorly truncated occipital shield; – Balaenoptera acutorostrata , in its smaller size, apex of the occipital shield narrow and only 10% of bizygomatic width (25% bizygomatic width in B.acutorostrata ), lacking a lateral triangular extension of the parietal between the squamosal and nuchal crest, exhibiting a ventrolaterally sloping (rather than vertical) surface of the parietal and frontal lateral to the supraorbital process of the frontal, transversely oriented anterior margin of the supraorbital process of the frontal in dorsal aspect (as opposed to being posterolaterally oriented), and a blunt distal apex of the inflated compound posterior process of the petrotympanic; – Balaenoptera bonaerensis Burmeister, 1867, in its smaller size, apex of the occipital shield narrow and only 10% of bizygomatic width (22% bizygomatic width in B. bonaerensis ), exhibiting a ventrolaterally sloping (rather than vertical) surface of the parietal and frontal lateral to the supraorbital process of the frontal, and transversely oriented anterior margin of the supraorbital process of the frontal in dorsal aspect (as opposed to being posterolaterally oriented), and a blunt distal apex of the inflated compound posterior process of the petrotympanic; – Balaenoptera borealis Lesson, 1824, in its much smaller size, apex of the occipital shield narrow and only 10% of bizygomatic width (26% bizygomatic width in B. borealis ), exhibiting a ventrolaterally sloping (rather than vertical) surface of the parietal and frontal lateral to the supraorbital process of the frontal, shorter and blunt zygomatic process of the squamosal, shallower squamosal crease, a more posteriorly projecting postglenoid process, a supraorbital process of the frontal that lacks a dorsal ridge, with a more concave lateral margin and transversely oriented anterior margin, larger occipital condyles, a much larger petrosal fossa, and a blunt distal apex of the inflated compound posterior process of the petrotympanic; – Balaenoptera edeni Anderson, 1879, in its much smaller size, apex of the occipital shield narrow and only 10% of bizygomatic width (18% bizygomatic width in B. edeni ), larger occipital condyles, shorter zygomatic process of the squamosals, a more laterally prominent preorbital process, exhibiting a ventrolaterally sloping (rather than vertical) surface of the parietal and frontal lateral to the supraorbital process of the frontal, supraorbital process of the frontal that lacks a dorsal ridge, and a blunt distal apex of the inflated compound posterior process of the petrotympanic; – Balaenoptera musculus Linneaus, 1758, in its much smaller size, in having a supraoccipital that is more broadly triangular with horizontal (rather than dorsolaterally) nuchal crests that dorsally overhang the temporal fossa, apex of the occipital shield narrow and only 10% of bizygomatic width (22% bizygomatic width in B. musculus ), exhibiting a ventrolaterally sloping (rather than vertical) surface of the parietal and frontal lateral to the supraorbital process of the frontal, shorter zygomatic process of the squamosal that is anteriorly directed (rather than anterolaterally directed), larger petrosal fossa and occipital condyles, posteriorly directed postglenoid process (not posterolaterally directed as in B. musculus ), a supraorbital process of the frontal with transversely oriented anterior margin and posterolaterally oriented posterior margin (as opposed to posterolaterally and posteromedially, as in B. musculus ) and a blunt distal apex of the inflated compound posterior process of the petrotympanic; – Balaenoptera omurai Wada, Oishi & Yamada, 2003, in its smaller size, in having a shorter and blunt zygomatic process of the squamosal, apex of the occipital shield narrow and only 10% of bizygomatic width (24% bizygomatic width in B. omurai ), a more transversely oriented anterior margin of the supraorbital process of the frontal (as opposed to posterolaterally as in B. omurai ), exhibiting a ventrolaterally sloping (rather than vertical) surface of the parietal and frontal lateral to the supraorbital process of the frontal, in lacking a sheet of the parietal that medially overlaps the supraorbital process of the frontal, and possessing a blunt distal apex of the inflated compound posterior process of the petrotympanic; – Balaenoptera physalus Linneaus, 1758, in its much smaller size, apex of the occipital shield narrow and only 10% of bizygomatic width (25% bizygomatic width in Balaenoptera physalus ), exhibiting a ventrolaterally sloping (rather than vertical) surface of the parietal and frontal lateral to the supraorbital process of the frontal, zygomatic process of the squamosal that is shorter and blunt, transversely narrower postglenoid process, a transversely oriented anterior margin of the supraorbital process of the frontal (as opposed to posterolaterally as in B. physalus ), larger petrosal fossa, and a blunt distal apex of the inflated compound posterior process of the petrotympanic; – Balaenoptera siberi Pilleri & Pilleri, 1989, in possessing an anteriorly truncated and narrow apex of the occipital shield, only 10% of bizygomatic width (18% bizygomatic width in B. siberi ), a squamosal crease, an anteriorly directed zygomatic process with a supramastoid crest that does not extend to the zygomatic apex, a zygomatic process that is dorsoventrally thicker, a paroccipital process that is less posterolater - ally directed and not as prominent posteriorly, well defined crease between the squamosal and paroccipital process, and a transversely oriented anterior margin of the supraorbital process of the frontal; – Cetotheriophanes capellinii (Brandt, 1873), in having a broader apex of the occipital shield that measures 10% of bizygomatic width (4% in C. capellinii ) that is anteriorly truncated, a shorter intertemporal region, a more anteriorly thrusted occipital shield, a shorter zygomatic process of the squamosal, and A longer postglenoid processes of the squamosal that are visible in dorsal aspect; – Diunatans luctoretmurgo Bosselaers & Post, 2010, in having a narrow apex of the occipital shield measuring only 10% of bizygomatic width (24% bizygomatic width in D. luctoretmurgo ), more sinuous lateral margin of the occipital shield, a slightly narrower zygomatic process that is less laterally offset from the braincase, pterygoid that is ventrally flat and not ventrally rounded in lateral aspect, and a posterior process of the petrotympanic that is anteromedially curved; – Megaptera novaeangliae Brisson, 1762, in its much smaller size, in having a squamosal crease, shorter and more anteriorly oriented zygomatic process that lack a supramastoid crest that extends to the zygomatic apex, transversely narrow and posteriorly projecting postglenoid process of the squamosal, a less transversely and anteroposteriorly broad supraorbital process of the frontal, a transversely oriented anterior margin of the supraorbital process (as opposed to posterolaterally oriented), anteriorly truncated and narrow apex of the occipital shield measuring only 10% of bizygomatic width (14% bizygomatic width in M. novaeangliae ), large petrosal fossae, and occipital condyles that are not set out on a distinct neck – “ Megaptera ” hubachi Dathe, 1983, in having a squamosal crease, shorter and more anteriorly oriented zygomatic process that lacks a supramastoid crest that extends to the zygomatic apex, a more anteriorly thrust occipital shield with a slightly transversely narrower apex measuring 10% of bizygomatic width (compared to 14% in “ M. ” hubachi ), an occipital shield that laterally overhangs the temporal fossa to a greater degree, a well defined crease between the paraoccipital process of the exoccipital and the squamosal, transversely narrow and posteriorly elongate postglenoid process of the squamosal, a laterally prominent antorbital process of the frontal, transversely oriented anterior margin of the supraorbital process, an inflated posterior process of the petrotympanic, and by lacking paired tuberosities on the supraoccipital and an anterior indentation in the apex of the occipital shield; – “ Megaptera ” miocaena Kellogg, 1922, in its smaller size, in having a squamosal crease, shorter and more anteriorly oriented zygomatic process that lacks a supramastoid crest that extends to the zygomatic apex, less anteriorly thrust oc- cipital shield that is roughly triangular and with more widely diverging lateral margins, vertex that is more anteriorly constricted and transversely narrower and measuring 10% of bizygomatic width (compared to 21% in “ M. ” miocaena ), an anteroposteriorly broader supraorbital process of the frontal lacking a posterolaterally oriented ridge on its dorsal surface and with a laterally prominent antorbital process, a planar and transversely oriented posterior margin of the supraorbital process of the frontal, a well defined crease between the paroccipital process and squamosal, and an occipital shield that is dorsally convex in lateral aspect; – Parabalaenoptera baulinensis Zeigler, Chan & Barnes, 1997, in having a squamosal crease, shorter and more anteriorly oriented zygomatic processes that lack a supramastoid crest that extends to the zygomatic apex, a clearly defined crease between the paroccipital process of the exoccipital and the squamosal, transversely broader apex of the occipital shield that measures 10% of bizygomatic width (8.7% in P. baulinensis ) large occipital condyles, transversely oriented anterior and posterolaterally oriented posterior margin of the supraorbital process of the frontal (posterolaterally and posteromedially oriented in Parabalaenoptera Zeigler, Chan, & Barnes, 1997, respectively), anterolaterally oriented nuchal crests (oriented dorsolaterally in Parabalaenoptera ), and a transversely narrow and posteriorly elongate postglenoid process of the squamosal; – Plesiobalaenoptera quarantellii Bisconti, 2010, in having a less elongate and more inflated and anteromedially curved posterior process of the petrotympanic; – Protororqualus cuvieri (Fischer, 1829), in having a squamosal crease, shorter and more anteriorly oriented zygomatic process that lack a supramastoid crest that extends to the zygomatic apex, a supraoccipital apex that is anteriorly squared-off at the vertex and transversely wider, measuring 10% of bizygomatic width (compared to 5% in P. cuvieri ), little to no parietal exposure at the vertex, laterally prominent antorbital process, and a posteriorly elongate postglenoid process of the squamosal. DESCRIPTION Ŋe holotype is a partial skull including a nearly complete braincase, complete left squamosal and frontal, and vomer; the maxillae, premaxillae, and nasals are missing as well as both right and left tympanic bullae and petrosals (with the exception of the posterior processes; Figs 11-15). Measurements of the holotype are presented in Table 6. UCMP 219078 was found upside-down, and many bones of the ventral portion of the skull (as well as the left supraorbital process of the frontal) are fractured and displaced (Fig. 16). Ŋe vomer is broken posteriorly, and is rotated anterodorsally (Fig. 13). Ŋe left supraorbital process exhibits a long, anterolaterally oriented fracture, and the portion of the bone lateral to this fracture has rotated so that the supraorbital process is oriented dorsolaterally, and the postorbital process is no longer in contact with the zygomatic process. A reconstruction of the skull of B. bertae n. sp. is depicted in Figure 17. Occipital shield In dorsal view the occipital shield is broad and triangular with a transversely narrow apex that is rectilinear and transversely oriented in dorsal view (Figs 11A, 15A). Ŋe anteriormost portion of the shield is longitudinally concave, and posterior to this, it is dorsally strongly convex along the sagittal plane. A pair of faint tubercles occur in the mid- dle of the supraoccipital, anterior to each occipital condyle. Ŋe nuchal crests are formed dorsally by the supraoccipital, are oriented anterolaterally, and overhang the temporal fossa so that the medial wall of the temporal fossa is not visible in dorsal aspect. Exoccipital Ŋe posterior margin of the exoccipital is posterolaterally oriented (Figs 11A, 12A). In dorsal view, the lateral margin of the occipital shield is slightly sinuous. Ŋe occipital condyles are relatively large. Ŋere are no clear dorsal condyloid fossae. Ventral to the foramen magnum, a shallow furrow extends between the occipital condyles. Squamosal Ŋe squamosal has a posteriorly elongate postglenoid process that is paddle-shaped (in dorsal and ventral view), dorsoventrally compressed, and posteroventrally directed (Figs 11B, 13A, 15C). Ŋe posterior margin of the postglenoid process is semi-circular in dorsal aspect. In lateral aspect, the ventral border of the mandibular fossa is strongly concave (Fig. 13), and both the zygomatic and postglenoid processes are somewhat ventrally directed, and in dorsal and ventral aspect, the zygomatic process is nearly anteriorly directed (Figs 11, 12). Ŋe zygomatic process is relatively short, blunt, and triangular in crosssection. Ŋe supramastoid crest runs along the dorsal margin of the squamosal from the lateral margin of the occipital shield, but does not extend far onto the zygomatic process. A distinct dorsoventrally oriented and anteriorly facing squamosal crease occurs on the anterior surface of the squamosal, at the base of the zygomatic process. Along the posteromedial wall of the temporal fossa near the parietal-squamosal suture, a faint squamosal cleft occurs and runs parallel to the parietal-squamosal suture. In dorsal aspect, postglenoid process terminates well anterior to the exoccipital. A vertical crease occurs at the squamosal-exoccipital suture at the posterolateral edge of the cranium (Fig. 11A). Ŋe posterolateral surface of the squamosal is relatively planar. Ventrally, the mandibular fossa is transversely broad, and anteroposteriorly concave. Basicranium Portions of the basicranium are badly shattered (Figs 11B, 12B). Ŋe posterior sheet and wings of the vomer and palatines are broken. Ŋe basioccipital is broad and shallowly concave between the relatively small and knoblike basioccipital crests. Ŋe basioccipital crest is elongate and transversely convex. Ŋe petrosal fossa is large, subrectangular, anteriorly bordered by the pterygoid, medially by the medial lamina of the pterygoid, laterally by the squamosal, and posteriorly by the exoccipital (Figs 11B, 12B, 15C). Ventrally, the exoccipital forms a transversely oriented ridge that is posterolaterally directed. Posterolaterally, the exoccipital contacts the posterior surface of the posterior process of the petrotympanic. Ŋe posterior process of the petrotympanic curves anteromedially, is distally swollen, and bears a sharp ventral crest (Fig. 15B, C). Ŋe posterior meatal crest anteriorly overlaps the posterior process of the petrotympanic, and anterior to this thin plate, the squamosal exhibits a posterolaterally directed, trough-like ext : Published as part of Boessenecker, Robert W., 2013, A new marine vertebrate assemblage from the Late Neogene Purisima Formation in Central California, part II: Pinnipeds and Cetaceans, pp. 815-940 in Geodiversitas 35 (4) on pages 836-852, DOI: 10.5252/g2013n4a5, http://zenodo.org/record/4538200 : {"references": ["MEAD J. G. & FORDYCE R. E. 2009. - Ne therian skull: a lexicon with emphasis on the odontocetes. Smithsonian Contributions to Zoology 627: 1 - 248.", "BOSSELAERS M. & POST K. 2010. - A new fossil rorqual (Mammalia, Cetacea, Balaenopteridae) from the Early Pliocene of the North Sea, with a review of the rorqual species described by Owen and Van Beneden. 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