Thylacinus breviceps Krefft, 1868a

Parnaby, Harry E., Ingleby, Sandy & Divljan, Anja, 2017, Type Specimens of Non-fossil Mammals in the Australian Museum, Sydney, Records of the Australian Museum 69 (5), pp. 277-420 : 300-303

Thylacinus breviceps Krefft, 1868a

Ann. Mag.Nat. Hist. (ser. 4) 2: 296, plate xvii. (October 1868).

Common name. Thylacine, the “Bull dog thylacine” of Krefft.

Current name. Thylacinus cynocephalus ( Harris, 1808) , following Jackson & Groves (2015).

Syntype. PA.774 by subsequent determination. Skull ( Fig. 3 ), subadult, sex not recorded. “ Thylacinus breviceps ” is written on the frontal bone but authorship is unknown. The original Palmer Register entry (written by Palmer and entered c. 1879) is “ Thylacinus cynocephalus , skull, Tasmania”. The register has subsequently been amended with “ Coll. Masters 1866? C/40/66”, most likely during preparation of the X Register in c. 1907. The AM Archives document C:40.66.07 ( AMS7 Letters Received ) is a list of specimens collected from Tasmania by George Masters. Note that uncertainty surrounds whether the document is correctly associated with the specimen, not merely the collection date.

Possible Syntypes. (2). One or other of the following two specimens are equally likely to be the remaining syntype: M.8331, matching left and right dentaries ( Fig. 4 ), right dentary marked “ Thylacinus breviceps . Right lower j.” in ink in old style handwriting; immature, sex not recorded, cranium not located. These were registered as “mandible only” on 22 March 1963. The whereabouts or fate of the matching cranium is unknown; there was no record of it when the dentaries were registered. Holes drilled through condyles indicate former attachment to a cranium. There are no associated data on collector, collection date or locality. PA.778, skull, immature, sex not recorded; registration details as for PA.774 and also marked as “Coll. Masters 1866? C/40/66”.

Condition. PA.774: Cranium: in good condition; subadult status indicated by third molars not fully erupted and basicranial sutures still visible; there is a hole in the left parietal bone (possibly a bullet hole) and in the left interparietal bone; drill holes for wiring the cranium and mandible together are present in the posterior ends of the zygomatic arches and condyles of the dentaries. Dentaries: good condition, third molar fully erupted and fourth partially erupted. PA.778: Cranium and dentaries in good condition. Cranium missing (lost) right M 2, left M 3 detached from skull. Cranium and dentaries were wired together in the past (drill holes remain). M.8331: Both dentaries are in good condition and are wired together below the 1st premolars; subadult with last molars not fully erupted.

Cranial measurements (mm). PA.774: GL, 171.92; ConL, 171.92; BasL, 161.16; NasL, 65.24* (nasal tips worn); NasB; 20.11; UC1–C1 (alv.), 31.10; APV, 12.80; PPV, 19.41; PAL, 96.38; UPM (alv.), 11.56; UMR (alv.), 39.08* (M 1 to the partly erupted M 3, does not include socket of M 4); ZB, 97.40; POC, 31.77; BUL, 13.29; MB, 56.43; DL (angl.), 138.55; DL (condyl.), 140.56; LPM (alv.), 12.62; LMR (alv.), 52.10. PA.778: GL, 160.23; ConL, 160.23; BasL, 150.01; NasL, 53.06; NasB; 18.73; UC1–C1 (alv.), 26.41; APV, 11.92; PPV, 18.88; PAL, 92.25; UPM (alv.), 11.06; UMR (alv.), 35.62* (M 1 to the partly erupted M 3, does not include socket of M 4); ZB, 86.21; POC, 27.77; BUL, 12.5; MB, 51.09; DL (angl.), 126.78; DL (condyl.), 127.48; LPM (alv.), 11.35; LMR (alv.), 46.67 (M 4 not erupted). M.8331: DL (condyl.), 135.51; LPM (alv.), 12.29; LMR (alv.), 49.13 (M 1 to M 3) [* = estimate].

Type locality. Ouse River , Tasmania ( Krefft, 1871a) .

Comments. Krefft (1872d) explicitly states that “The description of this … species is based on two skulls obtained by Mr Masters” and that “Both skulls are those of young animals, being about 7 1/ 2 inches long” (given as 6 5/8" in his original account). These were among a total of “about twenty six skulls” obtained by Masters and both specimens were “in possession of the Trustees of this Museum” ( Krefft, 1868a). The AM annual report for 1868 indicates that 25 Thylacine specimens were collected by Masters between December 1866 and March 1867 ( Krefft, 1868b); all of which are listed as Thylacinus cynocephalus with no further details.

Ride (1964) lists 774 as being Krefft’s original material but Krefft’s second skull has remained unidentified (Mahoney & Ride, 1988a). In his original account, Krefft states that he had sent photographs of both specimens of breviceps and location of these images, if they still exist, might resolve the identity of his second syntype. We are confident that cranium PA.774 is one of Krefft’s original specimens. The skull illustrations accompanying the original description, drawn from photographs sent by Krefft to London, show features that are consistent with the skull of PA.774, viz., two indentations on the upper left rear cranial vault (evidently from gun pellet impacts) and the shape of the left side of the paroccipital process. The dentaries associated with PA.774 seem to be a good match and the last molars are at an equivalent stage of eruption to those figured in Krefft’s original account. The remaining syntype is equally likely to be either PA.774 or M.8331, the difficulty being that it is not known how many specimens were assigned by Krefft to breviceps at the time of his eviction in September 1874, or if further specimens were labelled “breviceps” by subsequent workers. We have not established the sex of PA.778. This might be established by comparison with measurements of subadults of known sex. Dentaries could have been mismatched with crania in the past. However, both mandibles PA.778 and M.8331 are too short to match cranium PA.774 and the lower forth molars of both specimens are also at an earlier stage of eruption than that depicted in Krefft’s account.

bar (Photography by Stuart Humphreys); (c) 19th century writing on right dentary (Photography by HEP).

We have not identified who wrote breviceps on M. 8331 in ink in old style writing, nor for “breviceps” written in pencil on crania PA.774 and PA.778 but the latter two appears to be written by one person. Holes drilled through the condyles of M.8331 suggest that a skull did exist, but there are currently no subadult Thylacine skulls without dentaries in the AM Collection that match M.8331. We have not checked the Macleay Museum, which houses several Thylacine skulls obtained by Masters, for a possible match. It is most likely that Krefft’s syntypes comprised cranial material only, without skins. In his original description, Krefft (1868a: 297) states that Masters had collected “about 26 skulls, two of which … belong to breviceps ” and later ( Krefft, 1871a) states “this species has been founded on two skulls obtained by Mr Masters from the Ouse River.”, which he repeated in a newspaper account ( Krefft, 1872d).

Krefft maintained confidence in the validity of breviceps for some time after publication of his description in 1868 (e.g., Krefft, 1872d), and stated that his proposed diagnostic criteria for breviceps held when comparisons were made with immature skulls of cynocephalus ( Krefft, 1871a) but he did not specifically address the issue of sexual size dimorphism. He also claimed that he had support for his view that breviceps was a valid species from prominent anatomist Richard Owen ( Krefft, 1871a).

Figures

Figure 3. AM PA.774, syntype skull of Thylacinus breviceps Krefft, 1868a. (Photography by Stuart Humphreys).

Figure 4. Dentaries of AM M.8331, suspected syntype of Thylacinus breviceps. Krefft, 1868a: (a and b), with scale