Structure of the female reproductive tract of an adult parous Tasmanian tiger, Thylacinus cynocephalus

The present observations on the now-extinct Thylacinus are based on the rep roductive system of an adult thylacine discovered among the specimens of th e Hill collection at the Hubrecht Laboratory in the Netherlands. As in othe r marsupials, the reproductive tract was characterised by the presence of a uterus duplex and a vaginal complex where the ureters passed dorsally over each lateral vaginal canal to enter the bladder. The lateral vaginal canal s each entered a urogenital sinus that terminated in a shallow cloaca. The gross dimensions of the reproductive tract of the thylacine were greater th an those of any extant dasyurid marsupial. The distance from the rostral po le of the ovaries to the most caudal extremity of the urogenital sinus meas ured 25 cm. The distinctive aspects of the reproductive tract included a di sproportionate enlargement of the corpus uteri that is without parallel in any other marsupial species. The bodies of the right and left uteri measure d 10.4 cm x 1.2 cm x 0.9 cm and 9.1 cm x 0.8 cm x 0.7 cm respectively. The rostro-caudal length of the right and left cervices measured 2.7 cm and 1.7 cm respectively. The cervical canals entered the vaginal complex by way of a thick median vaginal septum. The elongated caudal component of the vagin al culs-de-sac lacked a median vaginal septum. As in other dasyurid marsupi als, the lateral vaginae and associated vaginal complex were of diminutive proportions in relation to the typical marsupial pattern. The histology of the tract was remarkably good for tissue preserved since 1902 and indicated that the tissues were free of pathological changes. A characteristic marsupial pattern of ovarian folliculogenesis was evident where all but a thin peripheral zone of the cytoplasm of the primary oocyte became vacuolated during the pre-antral stage of ovarian follicle developm ent.