There's a 2016 study that states that Megalictis might actually be Jaguar-sized based on skull size. Comparing the linear measurements of the cranium and mandible of M. ferox with some extant and extinct carnivorans, the basicranial length of M. ferox is similar to that of Panthera onca (jaguar) and overlaps with C. lupus. It is thus the largest mustelid skull ever known, even larger than the Late Miocene giant mustelids, Ekorus, Eomellivora and Plesiogulo (Table 3). The skull is also very wide–its mastoid width approaches that of Ursus americanus (Black bear) and exceeds by far that of the largest extant mustelids, the felids P. onca and Puma concolor (cougar) and the extinct mustelids Eomellivora ursogulo and Plesiogulo (Table 3).
Here's a table (image is too big)
I would post the study on a link, but it is linked to another forum and I'm not sure if I'm allowed to do that so I'm just gonna post it here:
Citation: Valenciano A, Baskin JA, Abella J, Pérez-Ramos A, Álvarez-Sierra MÁ, Morales J, et al. (2016)
Megalictis, the Bone-Crushing Giant Mustelid (Carnivora, Mustelidae, Oligobuninae) from the Early Miocene of North America. PLoS ONE 11(4): e0152430. doi:10.1371/journal.pone.0152430
AbstractWe describe cranial and mandibular remains of three undescribed individuals of the giant mustelid Megalictis ferox Matthew, 1907 from the latest Arikareean (Ar4), Early Miocene mammal fauna of Nebraska, and Wyoming (USA) housed at the American Museum of Natural History (New York, USA). Our phylogenetic hypothesis indicates that Ar4 specimens assigned to M. ferox constitute a monophyletic group. We assign three additional species previously referred to Paroligobunis to Megalictis: M. simplicidens, M. frazieri, and “M.” petersoni. The node containing these four species of Megalictis and Oligobunis forms the Oligobuninae. We test the hypothesis that Oligobuninae (Megalictis and Oligobunis) is a stem mustelid taxon. Our results indicate that the Oligobuninae form the sister clade to the crown extant mustelids. Based on the cranium, M. ferox is a jaguar-size mustelid and the largest terrestrial mustelid known to have existed. This new material also sheds light on a new ecomorphological interpretation of M. ferox as a bone-crushing durophage (similar to hyenas), rather than a cat-like hypercarnivore, as had been previously described. The relative large size of M. ferox, together with a stout rostrum and mandible made it one of the more powerful predators of the Early Miocene of the Great Plains of North America.IntroductionMegalictis ferox Matthew, 1907 [1] is a giant mustelid of the subfamily Oligobuninae and belongs to the paraphyletic group of “paleomustelids” [2]. It lived in the Early Miocene during the late Arikareean Ar4 North American Land Mammal Age 22.7–18.5 mya [3, 4] of the central Great Plains of United States in the states of Nebraska, South Dakota, and Wyoming [1, 5–7]. The Ar4 lithostratigraphic units containing giant oligobunines have been revised. Hunt [8] named the Anderson Ranch Formation for the terminal formation of the Arikaree Group in Nebraska and Wyoming formerly referred to as the Upper Harrison beds of Peterson [5, 9] and the lower Marsland Formation of Schultz [10]. The Black Bear Formation replaces the upper Rosebud Formation of South Dakota [11].
Megalictis ferox [1] was described from the Black Bear Formation, Stanley County, South Dakota, USA. A second giant oligobunine, Aelurocyon brevifacies Peterson, 1907 [5], was described from the Niobrara Canyon Local Fauna, Anderson Ranch Formation in Sioux County, Nebraska, USA. Hunt and Skolnick [7] established that the actual publication date for A. brevifacies was one week after Matthew described
M. ferox in 1907, not in 1906 as indicated in the journal. After these initial descriptions, Riggs [6] described new cranial and postcranial material of both taxa. Hunt and Skolnick [7] synonymized
Megalictis ferox, Aelurocyon brevifacies, and the large oligobunine mustelid
Paroligobunis simplicidens (Peterson, 1907) [5].
Here, we describe an important unpublished sample of craniomandibular remains of
Megalictis ferox (F:AM 25430, F:AM 54079, and AMNH 54076), housed at the American Museum of Natural History (New York, USA). Although F:AM 25430 and F:AM 54079 were found in the late 1930s and have been used to obtain metric, morpho-functional and phylogenetic data (e.g., [2, 7, 12–16]), they have never been fully described. Therefore, the main objective of the present paper is to describe these unpublished skulls and mandibles, and provide new data on the taxonomy and systematics of the genus in order to shed new light on the paleobiology of Megalictis.
Material and Methods
Nomenclature and MeasurementsDental nomenclature follows Ginsburg [17] and Smith and Dodson [18]. Anatomical descriptions are based primarily on Scapino [19], Turnbull [20], Barone [21, 22], Waibl et al. [23], Evans and de Lahunta [24, 25], and Hartstone-Rose et al. [26]. The terminology conforms to the standard of the Nomina anatomica Veterinaria [23] with the exception of the masseter and temporalis muscle complexes for which we follow Hartstone-Rose et al. [26]. The Megalictis material (Figs 1–4) has been compared to all the other material of Megalictis and Paroligobunis on the basis of published descriptions, figures, measurements and photographs. We have re-measured the dentition of AMNH 12880 and 22632 (cast of CM 1590) measured initially by Matthew [1] and Peterson [5] and completed the measures of Paroligobunis petersoni Loomis, 1932 [27] using a cast TMM 40966–1. Measurements were made using Mitutoyo Absolute digital calipers to the nearest 0.1 mm (Tables 1 and 2).
Fig 1. Cranium F:AM 25430 of Megalictis ferox.A lateral view; B rostral view; C dorsal view; D caudal view; E ventral view. Scale bar equals 5 cm.dx.doi.org/10.1371/journal.pone.0152430.g001
Fig 2. Mandible F:AM 25430 of Megalictis ferox.A Right mandible lateral view; B occlusal view; C Left mandible lingual view of lower dentition. Scale bar equals 5 cm.dx.doi.org/10.1371/journal.pone.0152430.g002
Fig 3. Cranium and mandibles remains of F:AM 54079 and AMNH 54076 of Megalictis ferox.A1–4 Cranium F:AM 54079, lateral view (A1), dorsal view (A2), ventral view (A3), and caudal view (A4); B1–3 right hemimandible F:AM 54079, lateral view (B1), medial view (B2), and occlusal view (B3); C1–3 left hemimandible F:AM 54079 lateral view (C1), medial view (C2), and oclussal view (C3); D1–3 right hemimandible of AMNH 54076, lateral view (D1), medial view (D2), and occlusal view (D3). Scale bar equals 5 cm.dx.doi.org/10.1371/journal.pone.0152430.g003
Fig 4. Crania of Megalictis ferox illustrating size differences.A, and B Megalictis ferox holotype AMNH 12880, lateral view (A), ventral view (B); C, and D Megalictis ferox CM 1590 (genotype of Aelurocyon brevifacies), lateral view (C), ventral view (D); Megalictis ferox F:AM 25430 lateral view (E), ventral view (F); G, and H Megalictis ferox F:AM 54079 lateral view (G), ventral view (H). Scale bar equals 5 cm. C and D courtesy of the Carnegie Museum of Natural History.dx.doi.org/10.1371/journal.pone.0152430.g004
Table 1. Upper tooth measurements (in mm) of Megalictis ferox.dx.doi.org/10.1371/journal.pone.0152430.t001
Table 2. Lower tooth measurements (in mm) of Megalictis ferox, Megalictis simplicidens, Megalictiss frazieri, and “Megalictis” petersoni.dx.doi.org/10.1371/journal.pone.0152430.t002Cladistic analysisIn order to better understand the phylogenetic relationships of the oligobunines
Megalictis ferox (AMNH 12880, CM 1590, F:AM 25430 and F:AM 54079),
M. simplicidens (=
Paroligobunis simplicidens) (CM 1553 and CM 2389),
M. frazieri (=
Paroligobunis frazieri) (UF 23928),
“M.” petersoni (=
Paroligobunis petersoni) (ACM 2011), and
Oligobunis crassivultus (AMNH 6903), we have performed a cladistic analysis (Fig 5) including 18 taxa (
M. ferox is represented in the analysis as 4 separate operational taxonomic units (OTU)) and 73 equally weighted and unordered craniomandibular characters (S1–S3 Appendices). Cladistic analysis was performed using in PAUP*4.0b10 [38]. The analysis was rooted using
C. lupus as the outgroup.
Fig 5. Phylogenetic relationships of Megalictis within Mustelidae.Searches were performed using the Branch and Bound and a Bootstrap analysis through 1000 replicates to test the clade support in the analysis. The outgroup was C. lupus. Strict consensus tree of 6 trees (Length 194 steps, consistency index (CI) = 0.41, retention index (RI) = 0.65) for knowing the relationships between the different specimens of Megalictis ferox, Megalictis simplicidens, Megalictis frazieri, “Megalictis” petersoni, Oligobunis crassivultus, and a sample of extant musteloids and a canid. Numbers below nodes are Bremer indices, and numbers above nodes are Bootstrap support percentages (only shown when ≥ 50). Character/taxa matrix is detailed in the S1–S3 Appendices. Silhouette of Megalictis ferox based on Hunt and Skolnick [7], silhouette of Megalictis simplicidens, Megalictis frazieri, “Megalictis” petersoni and Oligobunis crassivultus based on Megalictis ferox but rescaled according the size of the dentition.dx.doi.org/10.1371/journal.pone.0152430.g005Diagnosis: Large to giant size mustelid; robust mandible with a high, wide and distally curved ascending ramus; deep masseteric fossa with a stout crest that extends from the dorsal border of the coronoid process to below the m2; robust dentition; p1 present; p2–4 with distal cingula high-crowned; p4 relatively enlarged with mesial and distal accessory cuspids; m1 trigonid widened, with a strong lingual concavity between the paraconid and protoconid; m1 metaconid reduced to absent, present in the older and smaller forms and absent in the giant forms, m1 talonid low and narrow with a short, trenchant and labially located hypoconid; and m2 with reduced metaconid.
Type species: Megalictis ferox Matthew, 1907 p1.II, fig.1 [1]
Holotype: AMNH 12880, a partial reconstructed skull (Fig 4, S3 Video) with right P4, M1-2, a fragmented right mandible with almost complete coronoid process, m1 trigonid and m2, and very few postcranial remains figured by Matthew, 1907, p. 196, fig. 10–13, 15 [1].
Type Locality: Rosebud 22, Porcupine Butte, Black Bear Formation, Stanley County, South Dakota.
Other Localities: Rosebud 5, Porcupine Butte, Stanley County, South Dakota, USA (AMNH 12881); Niobrara Canyon Local Fauna, Sioux County, Nebraska, USA (CM 1590), “High Daemonelix beds”, Niobrara Canyon Local Fauna, Sioux County, Nebraska, USA (F:AM 25430); J-M District, South of Lusk, Goshen County, Wyoming, USA [6]; “high brown sand”, 16 Mile District, Goshen County, Wyoming, USA (F:AM 54079); 8 North of Lusk, Goshen County, Wyoming, USA (F:AM 54076).
Age: Upper part of the Anderson Ranch Formation and its equivalents, South Dakota, Nebraska, and Wyoming, late late Arikareean (Ar4), 22.7–18.5 mya [4] Early Miocene.
DiscussionMatthew [1] described and named the first specimens of
Megalictis ferox. The holotype is a fragmentary and reconstructed skull (Fig 4A and 4B, S3 Video), a partial mandible and some postcranial remains of a single individual (AMNH 12880). He [1] also described a second specimen (AMNH 12881) based on postcranial remains. Both individuals were found in two nearby localities (Rosebud 22 and Rosebud 5 respectively) at Porcupine Butte, South Dakota, USA, from the late late Arikareean (Ar4) Black Bear Formation. One week later [7], Peterson [5] named
Aelurocyon brevifacies (CM 1590) for the remains of a giant mustelid from the upper part of the Anderson Ranch Formation in Niobrara Canyon, Sioux County, Nebraska, based on more complete craniomandibular fossils (Fig 4C and 4D, S4 Video). Riggs [6] studied a large sample of Ar4 postcranial and some cranial material he termed A. brevifacies from the JM-District, south of Lusk, Wyoming, and some postcranial fossil of M. ferox from the Anderson Ranch Formation. Based on these and specimens from Beardog Hill, Agate Fossil Beds National Monument, Sioux County, Nebraska that had been assigned to Paroligobunis simplicidens [5, 29], Hunt and Skolnick [7] synonymized the oligobunines
Megalictis ferox, Aelurocyon brevifacies, and
Paroligobunis simplicidens into a single chronospecies
M. ferox. They [7] interpreted the differences observed in these three named taxa as attributable to individual and sexual variation and a slight degree of evolution over time. This hypothesis has been accepted by several authors (e.g., [3, 13, 42]).
Paleobiology of Megalictis feroxThe tendency towards gigantism in Mustelidae, the family that includes the smallest modern carnivoran (
Mustela nivalis), has occurred in different lineages throughout its evolutionary history. For example, Megalictis, Ekorus, Enhydriodon, Eomellivora, Ferinestrix, and Plesiogulo all exceed the size of the wolverine (
G. gulo), the largest extant terrestrial mustelid [1, 13, 32, 35, 37, 60, 61]. We have estimated the basal cranial length of the
M. ferox specimen AMNH-12880 based on the measurements of F:AM 25430 (Fig 4 and Table 3). Comparing the linear measurements of the cranium and mandible of
M. ferox with some extant and extinct carnivorans [13, 32, 33, 35 37, 62] (Table 3), the basicranial length of
M. ferox is similar to that of
Panthera onca (jaguar) and overlaps with
C. lupus. It is thus the largest mustelid skull ever known, even larger than the Late Miocene giant mustelids, Ekorus, Eomellivora and Plesiogulo (Table 3). The skull is also very wide–its mastoid width approaches that of
Ursus americanus (Black bear) and exceeds by far that of the largest extant mustelids, the felids
P. onca and
Puma concolor (cougar) and the extinct mustelids
Eomellivora ursogulo and Plesiogulo (Table 3). The average total mandible length of
M. ferox (Table 3) is the same as that of
P. onca and larger than
Eomellivora piveteaui, Ekorus, and
Plesiogulo crassa.
Table 3. Craniomandibular measures of Megalictis ferox and other giant mustelids and extant North American carnivorans.dx.doi.org/10.1371/journal.pone.0152430.t003Matthew [1] published a reconstruction of the skull and mandibles of
M. ferox AMNH-12880 that, in light of this study of new specimens, was clearly misinterpreted. His reconstruction has an overly-shortened rostrum and a very high forehead–all of which suggest a cat-like morphology (e.g., [7, 63, 64]). The F:AM 25430 specimen of
M. ferox has features that differ from Matthew’s reconstruction in its stouter premolars and molars, longer rostrum, and a smaller forehead. This morphology corresponds to a more bone-crushing hyena-like ecomorphotype, than Matthew’s more hypercarnivorous reconstruction suggests (Fig 9, S6 Video). That is, the dentition of
M. ferox represents that of a durophagous diet, more similar to that of, among extant mustelids, the wolverine [65]. The relatively blunt teeth (low Radius-of-Curvature) and low Intercuspid-Notch scores also support a relatively durophagous diet [66, 67]. The especially enlarged anterior edge of the Megalictis coronoid process, where the tendon of the M. temporalis is attached, could indicate adaptation for a wider gape. This feature, indicating emphasis on the longer anterior fibers of this muscle, is also present in hyaenids (Crocuta, Hyaena and Parahyaena) and jaguar (
P. onca), all carnivorans with powerful bite forces that eat larger prey [68]. This implies that the temporalis anchors more significantly on this anterior-most tendon as opposed to the central tendon or the bony faces of the coronoid process. This would allow the muscle fibers to be longer, thus allowing greater overall stretch of the muscle, which then allow greater overall gape [26]. This would be necessary in animals that eat larger prey, especially if they also have shorter faces (e.g., if the linear gape must be accomplished through radial rotation as opposed to elongation of the mandibles). However, this increase in fiber length comes at the cost of contractile force for a given muscle size–longer fibers have greater stretch but fewer of them can pack into the same volume of muscle thus resulting in a relatively reduced physiological cross-sectional area. Thus the temporal muscle in Megalictis appears relatively massive suggesting both great force production and gape abilities.
Fig 9. Sequential reconstruction of the head of Megalictis ferox based on F:AM 25430.A life appearance; B, reconstructed skull and mandible; C, Skull and mandible F:AM 25430. Artwork by Adam Hartstone-Rose.dx.doi.org/10.1371/journal.pone.0152430.g009Megalictis ferox shares several similarities with the smaller-sized
Enhydrocyon crassidens Matthew, 1907 [1], a wolverine-like hesperocyonine canid found in the same formation as M. ferox AMNH-12880, but in older sediments from the lower Arikareean. Both carnivorans have massive lower premolars, reduced upper molars, and zygomatic arches of similar shape and size. The similarities in morphology could indicate convergence in feeding habits. A hyena-like ecomorphotype also was developed in the North American borophagine canids, such as Aelurodon and the highly derived Borophagus, but did not appear until the beginning of the Barstovian (Middle Miocene) for Aelurodon and the Claredonian (Middle—Late Miocene) for Borophagus [69]. Due to the fact that M. ferox was restricted to the Arikareean, it would have been the best candidate for a hyena-like ecomorph because in general terms, canids of the time (e.g. Osbornodon and Cormocyon) had not yet evolved the battery of craniodental characteristics for crushing bones. With that said, although Megalictis did not have the extreme durophagous specializations of modern hyenas or fossil borophagines, they likely were more durophagous than the felid-like ecomporph to which they have been previously ascribed. The large-sized of M. ferox, together with a stout rostrum and mandibles, an enlargement of I3, a high cranium, and a raised nasal (Fig 9, S6 Video) suggest that it was one of the more powerful predators of the Lower Miocene (Arikareean 4) of the Great Plain of North America, coexisting with other large carnivorans including the amphicyonid Adilophontes and Daphoenodon [8] all of which likely consumed medium and large-sizes mammals including camels, horses and oreodonts [3].
ConclusionsThe new specimens of
Megalictis ferox described here (F:AM 54079, F:AM 25430 and AMNH 54076) give us a broader understanding of the morphology of
M. ferox and lead us to conclude that the holotypes of both
M. ferox (AMNH 12880) and
Aelurocyon brevifacies (CM 1590) are conspecific and thus the latter should be subsumed into
M. ferox. We argue that there are 3 species ascribed to Megalictis:
M. ferox, M. frazieri and
M. simplicidens. However, the fourth potential congener,
“M”. petersoni, might be best ascribed to a different genus. Our cladistic analysis suggests that
M. ferox is the sister taxon of the clade composed by
M. simplicidens—M. frazieri. Our phylogenetic hypothesis supports the subfamily Oligobuninae as being a stem mustelid.
The preservation of the of
M. ferox specimen F:AM 25430 represents by far the most complete and best preserved craniomandibular specimen of any giant mustelids. Based on the size of the skull, M. ferox emerges as the largest terrestrial mustelid ever known–even larger than the extinct Late Miocene giant mustelid Ekorus, Eomellivora, and Plesiogulo [13, 32, 33, 35, 37, 70]. This new material sheds light on a new paleobiological interpretation of Megalictis as a hyena-like, bone-crushing mustelid, instead of the cat-like ecomorphotype previously ascribed to the genus.
journals.plos.org/plosone/article?id=10.1371/journal.pone.0152430(I know that there still are pictures that are too big here but I'm just too lazy to fix the problem now. I'll post them on a link soon)
If Megalictis did reach this size, this match-up would be a bit of a mismatch in favour of Megalictis.
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Maybe the mustelid would have a slight edge at parity, given that these guys are pretty explosive and impressive. However, the wolf doesn't need a large size advantage to win.