Quinkana is an extinct group of crocodile-like reptiles that lived in Australia from about 25 million years ago until around 10,000 years ago. Most of the fossils found so far are from Queensland. Scientists have identified four species, all named between 1981 and 1997. The best-known species are Q. fortirostrum, which is the type species, and Q. timara, a more slender species from the Miocene period. The other two species, Q. babarra and Q. meboldi, are from the Pliocene and Oligocene periods, but they are only known from a few poorly preserved bones. The name Quinkana comes from "Quinkans," a spirit from Gugu-Yalanji mythology.

Quinkana is most famous for its ziphodont teeth, which are curved, have ridges, and are flat on the sides, giving them a blade-like shape. However, these teeth have only been found in two species. The earliest form did not have ridges, and the holotype of Q. fortirostrum did not preserve teeth in its jaw. The group is recognized by its ziphodont teeth and a deep, wide skull that resembles those of other reptile groups, leading some scientists to incorrectly classify Quinkana with those groups. Quinkana is estimated to have been about 3 meters (10 feet) long and weighed around 200 kilograms (440 pounds). Some remains from the Pliocene suggest it might have been larger, but these estimates are based on incomplete fossils and comparisons to related species, as no complete Quinkana specimens have been found.

Scientists have debated whether Quinkana was land-dwelling or lived partly in water. Some studies compare its anatomy to other land-dwelling reptiles from the Mesozoic and early Cenozoic eras, suggesting it was terrestrial. The discovery of bones from a crocodile-like reptile with a pillar-erect stance in the same rock layers as Quinkana supports this idea, though there is no direct evidence to confirm it. Most researchers who study mekosuchine reptiles believe Quinkana was terrestrial, but others argue that its remains are often found near freshwater, which might suggest a different lifestyle. The role Quinkana played in Late Pleistocene ecosystems is also debated. Older studies claimed Australia’s predators were mostly reptiles, but other scientists note that Quinkana was rare compared to large marsupial predators like Thylacoleo.

Quinkana fossils are commonly found in sediments that preserve evidence of woodlands near water sources like ponds, streams, and billabongs. It survived a major dry period during the transition from the Late Miocene to the Early Pliocene but eventually disappeared by the end of the Pleistocene, between 40,000 and 10,000 years ago. The exact reasons for its extinction are unknown, but scientists think long dry periods may have dried up rivers and destroyed forests, leading to its extinction along with much of Australia’s megafauna.

History and naming

Quinkana is one of the first fossil crocodilians discovered in Australia. The earliest fossils linked to this genus were found in 1886 by Charles Walter De Vis in the Darling Downs region of Queensland. He named them Pallimnarchus pollens, but this name is now considered uncertain (nomen dubium). Research on Quinkana began in 1970 when Lyndsey Hawkins, a member of the Sydney University Speleological Society, discovered fossil material in the Tea Tree Cave, part of the Chillagoe caves in northern Queensland. The fossil, labeled AMF.57844, included a partial rostrum (snout) missing the tip and teeth. This rostrum had a deeper shape than modern crocodiles and showed tooth sockets that suggested ziphodont teeth, a feature not previously seen in Australian fossils. Scientists compared it to modern crocodylids and extinct groups like pristichampsines and sebecosuchians.

Additional fossils were found in the years following this discovery. In 1975, Michael Archer recovered a ziphodont crocodilian from the Texas Caves in southern Queensland, later called the Texas Cave crocodile. This specimen included a partial maxilla and other bone fragments described in 1977 by Max Hecht and Michael Archer. Other early finds included the Croydon specimens, Rosella Plains teeth (originally thought to belong to Megalania), Darling Downs teeth, and the Chinchilla jugal (named after the town of Chinchilla, Queensland). Most of these remains were isolated bones from the Pliocene and Pleistocene eras. Some were found near Lake Palankarinna in South Australia, though they were initially thought to be sebecosuchians.

Paleontologist Ralph Molnar described Quinkana as a genus in 1981, primarily based on the Chillagoe cave rostrum. He also studied other materials, such as the Chinchilla jugal and Darling Downs teeth. Molnar classified the Texas Cave crocodile as part of the genus but did not assign it to a specific species due to minor differences that might be due to growth stages. Most of the other materials showed similarities to Quinkana but were too incomplete to be linked to Quinkana fortirostrum specifically. Molnar discussed Quinkana’s possible relationship to other crocodilians and its ecology, suggesting it might have been a land predator. He also proposed a possible connection between Quinkana and the European Pristichampsus.

In the 1990s, understanding of Australasian fossil crocodilians improved, and species were classified into the subfamily Mekosuchinae in 1993. In 1994, paleontologist Dirk Megirian named Quinkana timara as a second species within the genus. The holotype (NTM P895-19) included snout fragments from the Bullock Creek Locality in the Northern Territory. Megirian also linked other fossils from the same site to this species.

Two years later, Quinkana babarra was described by Brian Mackness and Paul M.A. Willis. The holotype (QM F23220), a maxilla fragment, was found in 1991 at the Dick’s Mother Lode Quarry in northeast Queensland. This species was more fragmentary than earlier ones, leading Willis and Mackness to revise earlier descriptions of Quinkana, removing features like prominent knobs near the eyes. In 1997, Quinkana meboldi was named by Willis based on maxillary fragments and a partial dentary from the White Hunter Site in the Riversleigh World Heritage Area, along with other mekosuchines like Baru wickeni, Baru huberi, and Mekosuchus whitehunterensis.

After these discoveries, fewer notable fossils were found. Scientists focused more on Quinkana’s ecology and whether it lived on land. A significant later find was a ziphodont tooth from the Late Pleistocene King Creek catchment in the eastern Darling Downs, a region known for Megalania fossils. This marked the first Late Pleistocene Quinkana material found there since 1981.

The genus name Quinkana comes from the Quinkans, spirits of the Gugu-Yalanji people of northern Queensland. Molnar chose this name partly because Quinkans were depicted as crocodiles in a rock painting in southeastern Cape York.

Species

• Quinkana fortirostrum
• Quinkana timara
• Quinkana babarra
• Quinkana meboldi

A major problem with much of this material is that it is often incomplete. Many of the finds are only single bones or parts of teeth. Because these remains are not complete and lack unique features, most cannot be clearly linked to any specific Quinkana species. However, sometimes the number of teeth ridges or the age of the fossils gives some clues about which group they might belong to. Other fossils not assigned to any of the four species include a partial upper jaw with two teeth (QM F10771) found at Glen Garland Station in Yarraden, northwestern Queensland. This fossil has tooth sockets similar to those of Quinkana babarra, but it is too incomplete to be certain. A tooth from the late Pleistocene (QM F57032) was discovered in 2013 at the Kings Creek site in southeastern Queensland. This tooth is similar to those usually linked to Quinkana fortirostrum, even though the main example of that species is actually toothless. Teeth have also been found in many other locations.

Sometimes, the differences in the material suggest the presence of species not yet named or even completely new groups. For example, in 1997, Paul Willis described a ziphodont crocodile from the Ongeva Local Fauna at the Alcoota Fossil Site that has not yet been named. A small land-dwelling mekosuchine from the middle Pleistocene Mt. Etna caves was mentioned by Sobbe and colleagues. Several isolated ziphodont teeth have also been found in the Otibanda Formation in Papua New Guinea. For the Otibanda finds, the material is currently labeled as ?Mekosuchinae gen. et sp. indet. because it is too incomplete for specific identification. The assignment to Mekosuchinae is based on the age and location of the fossils, not their physical features. Another discovery is the "Floraville taxon," which Jorgo Ristevski and colleagues suggest might be a second ziphodont genus besides Quinkana. Because many ziphodont crocodiles are likely different from Quinkana, Ristevski and colleagues argue that some teeth previously linked to Quinkana might actually belong to other groups.

A metatarsal bone (QM F30566) was found in 1992 at the Bluff Downs fossil site near Allingham in northern Queensland. This bone might be a rare limb part, but it could also belong to a different type of crocodile. Mackness and Sutton, who studied the material, suggested it did not belong to Quinkana babarra because that species is thought to have lived on land, though this is still debated. Another possible example of non-skull material was described by Stein et al. in 2017, who examined pelvic bones from the Golden Steph Site and Price is Right Site in the Riversleigh World Heritage Area. Like the metatarsal, there is no matching skull to confirm these fossils belong to Quinkana, but the physical features of the bones match what is commonly believed about the genus.

Description

Quinkana can be identified by the shape of its snout and its special teeth, which are often used as evidence that it lived more on land. The snout of Q. fortirostrum is deep and angular, similar to older crocodile-like animals from the Paleogene in the Northern Hemisphere and the Cretaceous to Miocene in South America. Molnar described the skull of Q. fortirostrum as broader than similar groups but much deeper than modern crocodiles, with a trapezoid shape when viewed from the side. However, the proportions varied among species. Q. timara, an older species from the Miocene, had narrower jaws similar to Boverisuchus. Q. meboldi also had narrow jaws, while Q. babarra had a shorter and broader snout than Q. fortirostrum.

The nostrils of Quinkana, unlike those of sebecosuchians, are similar to modern crocodiles, with a single opening directed toward the front and upward. However, in Quinkana, the nostrils are near the tip of the upper jaw and have deep notches, especially in Q. timara, making them more visible on the side of the skull. A ring of bone around the nostrils, called the narial rim, is weak in Q. timara but strong in Q. fortirostrum. The upper jaw bones form a small peg between the nasal bones and the maxillae. The nasal bones are paired, parallel, and tapering, entering the nostrils without forming a bridge between them. In profile, the nasal bones are slightly curved and sculpted, located entirely on the top of the skull, unlike sebecosuchians, where they form a central ridge on the sides. The maxillae are steep, giving Quinkana's skull a deep appearance. Near the front, they angle at 60°, while toward the back, they angle at 45°, with only slight sculpturing on their surface.

The lacrimal and prefrontal bones, located near the eyes, are shaped by the angular skull of Quinkana. The lacrimal contributes to the side of the skull, while the prefrontal is on the top, like the nasal bones. The shape of the lacrimal suggests Quinkana had sideways-facing eyes, a trait common in land-dwelling crocodile relatives. In Q. fortirostrum, the area below the eyes is poorly preserved, but other species provide clues. Initially, Molnar claimed the jugal bone (a cheek bone) did not extend in front of the eyes, but later studies showed it did in Q. timara and in a Texas Caves specimen. The inner contact between the maxilla and jugal suggests the outer suture was even further forward. The lower part of the jugal had a sculptured area like that of modern American alligators. The maxilla's depth indicates the infraorbital bar (the area below the eye sockets) was much deeper than usual. The postorbital bar, a bony peg behind the eyes, is more vertical in Quinkana than in flat-skulled species, suggesting the skull overhung the temporal region.

Quinkana's skull has distinct ridges, knobs, and protrusions. In addition to the narial rim and sculpted nasal bones, some species have a crest along the maxilla and sometimes the premaxilla. Q. fortirostrum has a rounded crest on both bones, while Q. timara's crest is only on the maxilla. Q. babarra had multiple isolated peaks instead of a full crest. More ridges appear where the maxilla transitions from its side to top surface. The lacrimal and prefrontal bones of Q. fortirostrum have knobs instead of ridges, a feature unique to Quinkana, with two knobs on the lacrimal and one on the prefrontal. These features are also present in older species but less pronounced. Megirian suggests age might influence these features, as they change as individuals grow. Quinkana also has a large antorbital shelf, a flat area near the eyes on the skull's top, which is larger in Q. timara.

The bottom of the maxilla is slightly curved and lacks the wave-like patterns (festooning) seen in many crocodiles. This is especially true in Q. fortirostrum, where the tooth row is nearly straight, though slightly more developed in Q. timara. Lateral festooning is also minimal, so Quinkana's skull does not have the wavy outline typical of other crocodiles. The only notch in Quinkana's skull separates the maxillae and premaxillae. The most noticeable festooning occurs in Q. babarra and Q. meboldi, though it is still faint.

Looking at the skull from below, the contact between the premaxilla and maxilla forms a U-shape, and the incisive foramen is wider than it is long. Differences in the palatines (roof of the mouth) and palatal fenestrae (openings) are also notable. In Q. fortirostrum, the palatines do not extend beyond the fenestrae as they do in many crocodiles, instead ending between them with a V-shaped suture. Molnar initially thought Quinkana lacked an anterior process (a bony extension), but Megirian described it as small in Q. fortirostrum and Q. timara. Similarly, Q. meboldi's palatine process is short.

Phylogeny

Quinkana is an ancient crocodile that lived long before many modern studies on crocodiles began. Early scientists were unsure how Quinkana was related to other crocodiles because not much research had been done on its family, the Mekosuchinae. The type species, Q. fortirostrum, was first classified in 1981 as part of the Crocodylidae family by comparing it to other crocodile groups like Pristichampsus, Paleosuchus, and Osteolaemus, as well as the Sebecosuchian genus Sebecus. Scientists found that Q. fortirostrum had the most similarities with Pristichampsus and placed it in the Eusuchia group. Similarities to Sebecus were not considered important because they were thought to be the result of similar traits developing independently. However, Quinkana had a unique snout shape and sharp, pointed teeth that set it apart from most other crocodiles, except for those in the Pristichampsinae group. Though Molnar did not officially place Quinkana in this group (now called Planocraniidae), he believed future discoveries might support this connection.

In the late 1980s and early 1990s, more crocodile fossils were found in Australia, helping scientists notice shared features among them. In 1993, Molnar, Willis, and Professor John Scanlon proposed the Mekosuchinae subfamily to classify these Australian crocodile species, including Quinkana. This group was meant for crocodiles with unique traits that lived in Australasia during the Cenozoic era. However, in 1994, Dirk Megirian suggested more research was needed to understand Quinkana’s relationship to other crocodiles, as its snout resembled those in the Crocodylidae family. Megirian was unaware of the Mekosuchinae classification at the time and only briefly mentioned it later. Willis later confirmed Quinkana’s placement in Mekosuchinae in 1995, even though it was the only member of the group with sharp, pointed teeth.

Since then, most scientists agree that Quinkana belongs to the Mekosuchinae family, especially as more fossils were discovered. However, its exact position within this group is still unclear and has changed over time. In 2018, Lee and Yates used data from physical traits, DNA, and fossil ages to study crocodile relationships. Their study placed Quinkana close to small crocodile species like Mekosuchus and Trilophosuchus. Another study by Jorgo Ristevski suggested Quinkana was more closely related to larger, generalist crocodiles like Paludirex and Baru. A third study by Yates and colleagues placed Quinkana between Kalthifrons and a group including Mekosuchus, Paludirex, and Baru.

While most scientists agree Quinkana is part of the Mekosuchinae family, some studies have proposed different classifications. In 2021, Rio and Mannion used only physical traits to study crocodile relationships, unlike Lee and Yates, who combined multiple types of data. This study found Quinkana was closely related to "Crocodylus" megarhinus, a species outside the modern Crocodylus genus. However, most Mekosuchinae researchers do not support these findings.

"Asiatosuchus" nanlingensis
Trilophosuchus rackhami
Mekosuchus whitehunterensis
Mekosuchus inexpectatus
Australosuchus clarkae
"Crocodylus" megarhinus

Paleobiology

The way of life and environment of Quinkana has been a topic of discussion among scientists since its first description by Molnar. He pointed out reasons that suggest Quinkana lived on land, but also noted possible arguments against this idea. For example, the main fossil sample of Q. fortirostrum was found in cave deposits, which some believe means the animal walked on land before dying. However, Molnar also noted that modern crocodiles sometimes travel on land as well. The place where the fossils were found does not clearly show whether Quinkana lived on land or near water. Many areas where Quinkana fossils were found also had remains of animals that lived on land and near water, similar to places where other crocodile-like animals are known to have lived on land. Later, Busbey in 1986 and Willis and Mackness in 1996 also agreed that Quinkana likely lived on land.

The way the fossils were preserved is less important than the physical structure of Quinkana. Scientists have long noticed that Quinkana looks similar to planocraniids, a group of land-dwelling crocodile relatives from the Paleogene period in Europe. These animals are known to have been major predators on land, with traits that suggest a life on land, which Quinkana also shares. Among Quinkana species, Q. timara has a skull shape most similar to planocraniids, while Q. fortirostrum has a much wider head. However, it is unclear how these differences affected Quinkana’s lifestyle. The shape of Quinkana’s teeth, which are similar to those of planocraniids and older crocodile relatives, is also a mystery. Molnar suggested that the teeth’s sharp edges and side compression might mean Quinkana hunted larger prey than typical crocodiles, but this does not show whether the prey was on land or in water. Molnar also said that Quinkana might have hunted other crocodiles or land animals. Later, Busbey compared Quinkana’s teeth to those of large, land-dwelling lizards like the komodo dragon. Willis agreed, saying Quinkana and large lizards might have hunted in similar ways. Stein et al. suggested that these teeth might have helped Quinkana chase prey actively, unlike modern crocodiles that usually ambush prey. Others, like Murray and Vickers-Rich, thought Quinkana might have waited near trails for prey instead of near water.

Many questions about Quinkana’s lifestyle could be answered if more bones from its body or limbs were found. Molnar noted that some ancient crocodile relatives were identified as land-dwellers based on body traits, such as hoof-like toes and a rounded tail instead of a flat, paddle-shaped tail seen in water-dwelling crocodiles. However, no bones from Quinkana’s body have been found, so scientists cannot directly see these traits. Other related animals, like Kambara, show traits that suggest better movement on land than modern crocodiles. Kambara, a well-preserved ancient crocodile relative, had strong leg bones that allowed it to move quickly and steadily, though it still lived near water. A 2017 study by Stein and colleagues examined bones from Quinkana’s habitat, including the Riversleigh area. They found different types of hip bones, with one type possibly belonging to Quinkana. This hip structure is similar to that of other land-dwelling crocodile relatives and might have helped Quinkana stand upright while moving, supporting a land-based lifestyle. However, more evidence is needed to confirm this connection.

Molnar suggested that Quinkana and Megalania, a giant lizard, might have been top predators in Australia during the Pleistocene, as Australia had few large land mammals compared to other continents. This idea became popular in the late 20th century, with some scientists saying Australia’s top predators were reptiles like Quinkana, giant lizards, and snakes, not marsupials. Others, like Max Hecht, argued that animals like Thylacoleo, a marsupial predator, could not have taken the place of large cats. Sobbe, Price, and Knezour also said that Australia’s ecosystems changed over time, with reptiles becoming more common as predators. However, Stephen Wroe questioned this idea in 2002, pointing out that reptile fossils are rare compared to those of marsupials. He also argued that Quinkana likely lived near water, not on land. Some of Wroe’s arguments, like the idea that certain features in crocodile fossils might be due to how they were preserved, have been challenged by experts like Christopher Brochu, who said these traits are real and suggest a land-based lifestyle. Later discoveries about Quinkana’s hip structure also support the idea of a land-dwelling lifestyle.

Living on land and being near water may not be completely separate. Some scientists, like Willis and Wroe, suggest that Quinkana might have hunted on land but returned to water for safety, to regulate body temperature, or for reproduction.