Mammalia, Linnaeus, 1758

Price, Gilbert J., Cramb, Jonathan, Louys, Julien, Travouillon, Kenny J., Pease, Eleanor M. A., Feng, Yue-Xing, Zhao, Jian-Xin & Irvin, Douglas, 2020, Late Quaternary Fossil Vertebrates of the Broken River Karst Area, Northern Queensland, Australia, Records of the Australian Museum 72 (5), pp. 193-206 : 198-202

Mammalia

Marsupialia

Dasyuridae

Dasyurus sp. indet. ( Fig. 5A ). A medium-sized quoll is represented by isolated molars. Dimensions of the molars indicate that it is within the size range of D. viverrinus and D. geoffroii , but the available material is insufficient to separate these species.

Antechinus sp. indet. ( Fig. 5B ). The identification of fossil Antechinus is discussed in Cramb & Hocknull (2010a). Antechinus is a rare taxon at Broken River, represented by mandibular fragments and isolated teeth. Most species of Antechinus have posterior cingula on M 1-3, and this is the distinguishing feature of the Broken River specimens. The exact identity of the Broken River specimens cannot be established on the basis of available material.

Phascogale tapoatafa ( Fig. 5C ). The Brush-tailed Phascogale is a medium-sized dasyurid with a reduced P 3, posterior cingula on the upper molars, commonly buccal cingula on M 1, and relatively strong buccal cingulids on the lower molars. It is distinguished from other species ( P. pirata , P. calura , and an undescribed species from Mount Etna) by being larger and having stronger buccal cingula on the upper molars.

Planigale sp. cf. P. ingrami / tenuirostris ( Fig. 5D ). Archer’s (1976) revision of Planigale found that the most reliable dental features separating species were size and presence/ absence of a P 3 / 3. One specimen from Big Ho has a lower molar row measuring 4.05, within the ranges of P. ingrami and P. tenuirostris , and equidistant between the means for both species as given by Archer (1976).

Sminthopsis macroura ( Fig. 5E ). The Stripe-faced Dunnart is medium-size (for a species of Sminthopsis ), and possesses large entoconids on M 1-3 that do not contact the hypocristids ( Archer, 1981).

Sminthopsis sp. cf. S. murina ( Fig. 5F ). The majority of Sminthopsis specimens in the study sites lack entoconids on M 1-3. They are assigned to S. murina here, although distinguishing that species from other “entoconid-less” species of Sminthopsis is difficult ( Cramb et al., 2009).

Chaeropodidae

Chaeropus yirratji ( Fig. 5G ). Three specimens from Big Ho and four from Beehive represent the Northern Pig-footed Bandicoot and were included in the description of the species in Travouillon et al. (2019). Characters on the M 1 and M 1 are diagnostic and help separate it from Chaeropus ecaudatus . These include the paracone connecting to StB (stylar cusp B) only on M 1 (not StA, in unworn teeth); the metaconule on M 1-3 is well-developed, making molars more rectangular in shape; StD present on M 1 and the paracristid on M 1 does not connect to the protoconid (in unworn teeth).

Peramelidae

Isoodon sp. ( Fig. 5H ). This taxon is recorded only in Big Ho and is represented only by isolated lower molars (M 1 and M 2). All measurements are within the modern range for I. macrourus torosus , but at the smaller end of the range. There are very few diagnostic characters on lower molars of Isoodon . Despite being clearly a specimen of Isoodon , and being too large to be any other species than I. macrourus , there are a number of differences compared to the modern taxon. The paraconid on M 1 is large and in line with the metaconid (the paraconid is commonly reduced and more buccally positioned in all described species of Isoodon ). The posthypocristid is not perpendicular to the toothrow on either the M 1 or M 2, which is a feature typically seen in Isoodon auratus , I. fusciventer , and I. peninsulae but not in I. macrourus . It is an undescribed species of Isoodon . We do not erect a new species here, but rather wait on the discovery of additional, more comprehensively diagnosable material.

Isoodon peninsulae ( Fig. 5I ). The Cape York Brown Bandicoot is the most common species of bandicoot present in both Big Ho and Beehive. The dental measurements are slightly larger than the modern range for this taxon, but still below that of I. macrourus . The overall morphology matches that of I. peninsulae . It differs from I. auratus , I. fusciventer , and I. macrourus in having a preparacrista of M 1 buccally orientated then posterobuccally orientated. It differs from I. fusciventer and I. macrourus in having a stylar crest present on M 1 and no StC/D on M 4. It differs from I. fusciventer , I. macrourus , and I. obesulus in having a small anterior cingulum on M 1 not connected to the talon, and a large anterior cingulum of M 2 not connected to talon. It differs from I. macrourus and I. obesulus in having the posthypocristid of M 1 and M 2 oblique to the tooth row.

Perameles sp. ( Fig. 5J ). This taxon is only represented by two isolated molars, a left M 1 and a left M 2, both from Big Ho. The M 1 length is within the range of modern Perameles pallescens , but the tooth is wider than in the modern species. The M 2 width is also within the modern range, but the length is longer. The M 2 typically has no reliable characters to identify specimens to known species (see Travouillon, 2016). The M 1 has several characters which are diagnostic: it differs from Perameles bougainville , P. fasciata , P. myosuros , P. notina , and P. gunnii in having a short stylar crest not connected to StD. It differs from Perameles eremiana , P. fasciata , P. myosuros , P. notina , and P. papillon in that the preparacrista not reconnecting to the postparacrista posteriorly. It differs from Perameles bougainville , P. eremiana , P. fasciata , P. myosuros , and P. papillon in having StB and StC distinguishable with StC larger than StB. It differs from all Perameles except P. eremiana and P. nasuta in having a very small StA. It differs from P. nasuta and P. pallescens in having a postprotocrista that ends posteriorly to metacone. It differs from P. fasciata in having no anterior cingulum. While there are enough characters to separate it from all modern taxa, it is not described as a separate species here, as it cannot be compared to the extinct fossil species Perameles sobbei , from which no M 1 has been recovered to date. The M 2 matches the morphology of P. sobbei (e.g., Price, 2002), but it also matches that of other Perameles , such as P. pallescens . As a result, we consider this taxon as Perameles sp. until further material is recovered, but it is undoubtedly an extinct species.

Petauridae

Petaurus norfolcensis ( Fig. 6A ). The Squirrel glider is a medium-sized Petaurus distinguished by having molar rows longer than those of P. breviceps and P. biacensis but shorter than P. australis , P. gracilis , and P. abidi .

Phalangeridae

Trichosurus sp. indet. ( Fig. 6B ). Phalangerids are easily distinguished from similarly-sized pseudocheirids by their bunodont molars.

Few morphological characters separate the species of Trichosurus , but T. vulpecula is extant in the Broken River area and is thus considered to be the most likely identity of the fossil specimens. One specimen from Big Ho is an unerupted molar, indicating that the individual was a juvenile.

Hypsiprymnodontidae

cf. Hypsiprymnodontidae gen. et sp. indet. ( Fig. 6C ). An isolated premolar fragment has the distinctive “buzzsaw” shape and ridges seen in hypsiprymnodontids, some burramyids, and propleopines. The size of the specimen is similar to Hypsiprymnodon , but its generic and specific identity is unknown.

Macropodidae

Macropodidae indet. ( Fig. 6D ). Macropodid remains are uncommon, fragmentary, and appear to be from immature individuals. A partial mandible from Beehive represents a very young individual, most likely from a rock wallaby ( Petrogale sp. ) although additional material is required to confirm the identification.

Placentalia

Muridae

Rats and mice are most readily identified to species by their upper molars and maxillae, which form the majority of referred specimens here.

Conilurus albipes ( Fig. 7A ). Distinguishing features of the species are listed by Cramb & Hocknull (2010b). The Broken River sites are the northern-most records of this species.

Conilurus capricornensis ( Fig. 7B ). Isolated molar fragments from Big Ho are referred to a large species of Conilurus that has proportionally shorter, broader cusps than C. albipes . Of the three species, C. capricornensis is the best fit for these specimens. The type locality for the species is also in the Broken River area ( Cramb & Hocknull, 2010b).

Leggadina forresti ( Fig. 7C ). Distinguishing features for species of Leggadina are listed by Cramb et al. (2017).

Field guides (e.g., Menkhorst & Knight, 2010; Van Dyck et al., 2013) show the distributions of L. forresti and L. lakedownensis as non-overlapping, with the latter present in northeast Queensland. However, L. forresti is recorded as extant in the area so its palaeo-occurrence in the study sites is perhaps not surprising.

Notomys longicaudatus ( Fig. 7D ). The Long-tailed Hopping-mouse is identified by its large, Pseudomys -like molars; broad T8–9 complex on M 1; proportionally short molar row; concave anterior margin of zygomatic plate with associated spine; and deep zygomatic bar.

Notomys sp. 2 ( Fig. 7E ). This species was originally identified by Ken Aplin based on specimens from Christmas Creek (an unpublished collection from west of the study sites). It has since been found in other deposits in the Broken River area. It is a moderately large species that cannot be placed in any described species with confidence (Ken Aplin pers. comm., November 2009).

Pseudomys australis ( Fig. 7F ). The Plains Mouse is distinguished by having molars that are proportionally narrow, each tapering posteriorly; cusps taller than those of P. gracilicaudatus , but not as tall as P. oralis ; a T3 on M 1 that is heavily reduced or absent; accessory cusp absent; and a proportionally long M 3. The anterior palatal foramen is posteriorly narrow. Specimens from the study sites are among the northern-most records of this species.

Pseudomys sp. cf. P. delicatulus ( Fig. 7G ). Small species of Pseudomys are difficult to distinguish. Two species are known to occur in eastern tropical Queensland today: P. delicatulus and P. patrius . A maxilla from Big Ho preserves the posterior end of the anterior palatal foramen, which extends past the anterior margin of M 1. This suggests that it is probably P. delicatulus , although the presence of P. patrius , or other small species of Pseudomys , cannot be excluded.

Pseudomys desertor ( Fig. 7H ). An isolated M 1 is assigned to P. desertor due to its broad T4 and T8–9 complex, and straight posterior margin on the anterior loph.

Pseudomys gouldii ( Fig. 7I ). Gould’s Mouse is a medium-sized Pseudomys characterized by the following features of M 1: crown not as broad as P. gracilicaudatus , variably developed accessory cusp, commonly with a link between the bases of T1 and T2; reduced or absent T3; cusps of middle loph all well-defined; T4 noticeably larger than T1; and T8–9 tapering posteriorly. Several of these features are diagnostic of P. australis , but the fossils appear to be closer to P. gouldii in that they commonly have an accessory cusp; a less elongate M 3; and a posteriorly broader anterior palatal foramen.

Pseudomys gracilicaudatus ( Fig. 7J ). The Eastern Chestnut Mouse is a medium-sized mouse that has broad molars and commonly has a well-developed accessory cusp on M 1. It is very similar to P. nanus , leading Watts & Aslin (1981) to suggest that these two species are best separated by geographic distribution (a dubious proposition when applied to fossils). Known distributions of P. gracilicaudatus and P. nanus suggest that P. gracilicaudatus is the most likely species in the study sites.

Zyzomys sp. ( Fig. 7K ). A large species of rock rat is found in several cave sites in eastern Queensland. Godthelp (1997) stated that both Z. argurus and Z. woodwardi were present in the Chillagoe area until recently. However, examination of more complete specimens from Mount Etna has indicated that the larger species of Zyzomys found in eastern tropical Queensland sites is an undescribed species. It is identified in the study sites by the dimensions of M 1, which is larger than that of Z. argurus .

Hydromys chrysogaster ( Fig. 7L ). A single right M 2 is the only evidence of this species in the study sites. Isolated molars are easily recognized by their bulbous molar lophs with indistinguishable cusps. The single specimen here is unworn, indicating that it was a young individual.

Melomys cervinipes ( Fig. 7M ). Melomys and Uromys molars are distinguished by having well-developed lingual cusps on M 1-2 but lacking a T7; having more than three roots on M 1; molar cusps that seem to wear rapidly, so that most specimens exhibit joining of the cusps to form flat-topped lophs; and fine ornament on the molar enamel. Melomys cervinipes is distinguished from M. burtoni by being larger and having four roots on M 1. Melomys capensis also has four roots on M 1, and it is probably not possible to distinguish M. capensis and M. cervinipes on the basis of isolated molars. The specimens in Beehive are close to the mean M 1 width of M. cervinipes , and are also considered more likely to be this species on the basis of extant distributions.

Rattus sordidus / tunneyi / villosissimus / colletti group ( Fig. 7N ). Four of the seven indigenous species of Rattus form an obvious group based on morphology and molecular phylogenetics: R. sordidus , R. tunneyi , R. villosissimus , and R. colletti ( Aplin, 2006) . Molar measurements of species within this complex are similar, making identification of fossil specimens difficult.

Rattus lutreolus ( Fig. 7O ). Isolated molars of the Swamp Rat can be distinguished from other Australian species of Rattus by their larger size. One specimen from Beehive is a partial palate, with associated maxillae and palatines.

Miniopteridae

Miniopterus orianae ( Fig. 7P ). Diagnostic craniodental characters for Australian microbats are given by Martinez (2010). Multiple species of microbats are present in the study sites based on different sized limb elements, but only M. orianae is represented by generic and specific diagnostic craniodental material: a left maxilla with P 1-2 and M 1-3. Miniopterus orianae ( M. schreibersii in Martinez, 2010) is distinguished from M. australis by the larger dimensions of the M 1, particularly width.

Geochronology

We produced 10 U-Th dates ( Table 2) for two fossil bones ( Fig. 8 ), one each from Big Ho (broken cross-section of a femur) and Beehive (broken cross-section of a tibia). Uranium concentration is relatively consistent in both specimens (c. 7 ppm for Big Ho and 3.5 ppm for Beehive) regardless of proximity to the outer natural surface of the bones. Similarly, 230 Th ages are relatively consistent through both respective cross-sections. This suggests that both bones rapidly took up U following burial and both have acted as closed systems after recrystallization of the calcium phosphate; there is no evidence of U leaching. Thus, the dates for Big Ho (c. 165 ka) and Beehive (c. 8.5 ka) are reliable minimum ages and are most likely close to the burial ages of the collected portions of the respective deposits. Considering the shallow stratigraphic depth of the sampled portion of both deposits (i.e., 50–70 mm depth), lack of stratification, and no geological evidence of sedimentological hiatuses, it is unlikely that the breccias accumulated over long periods of time. Thus, we consider the ages as reliable approximations for the contained fossil assemblages from both respective breccias.

The hypothesized relative ages of the breccias as estimated by geological inferences is supported by direct U-series dating (i.e., that Big Ho is older). Both deposits are clearly late Quaternary, with Big Ho dating to the penultimate glacial cycle between Marine Isotope Stage (MIS) 7A and 6, while Beehive dates to the early Holocene (MIS 1).

Figures

Figure 5. Dasyurids and bandicoots of the Broken River karst area. (A) Dasyurus lower molar (UQPL10); (B) Antechinus sp. dentary (UQPL11); (C) Phascogale tapoatafa lower molar (UQPL12); (D) Planigale sp. cf. P. ingrami/tenuirostris dentary (UQPL13); (E) Sminthopsis macroura dentary (UQPL14); (F) Sminthopsis sp. cf. S. murina dentary (UQPL15); (G) Chaeropus yirratji maxilla (QMF58987); (H) Isoodon sp. lower molar (UQPL17); (I) Isoodon peninsulae mandible (UQPL16); (J) Perameles sp. upper molar (UQPL18). Scale bars = 1 mm.

Figure 6. Diprotodonts from the Broken River karst area. (A) Petaurus norfolcensis upper molar (UQPL19); (B) Trichosurus sp. upper molar (UQPL20); (C)?hypsiprymnodontid premolar (UQPL21); (D) juvenile macropodid mandible (UQPL22). Scale bars = 1 mm.

Figure 7. Placentals from the Broken River karst area. (A) Conilurus albipes maxilla (UQPL23); (B) Conilurus capricornensis molar fragment (UQPL24); (C) Leggadina forresti maxilla (UQPL25); (D) Notomys longicaudatus maxilla (UQPL26); (E) Notomys sp. 2 maxilla (UQPL27); (F) Pseudomys australis maxilla (UQPL28); (G) Pseudomys sp. cf. P. delicatulusmaxilla (UQPL29); (H) Pseudomys desertor molar (UQPL30); (I) Pseudomys gouldii maxilla (UQPL31); (J) Pseudomys gracilicaudatus maxilla (UQPL32); (K) Zyzomys sp. molar (UQPL33); (L) Hydromys chrysogaster molar (UQPL34); (M) Melomys cervinipes maxilla (UQPL35); (N) Rattus sp. maxilla (UQPL36); (O) Rattus lutreolus maxilla (UQPL37); (P) Miniopterus orianae maxilla (UQPL38). Scale bars = 1 mm.

Figure 8. U-series dated fossil samples from the Broken River karst area. (A) breccia karst from Beehive; (B) breccia clast from Big Ho.Arrows indicate dated specimens. Scale bars = 10 mm.