12. Trilophosuchus with Jorgo Ristevski

Crikey! Adele takes a trip in time to the Late Oligocene to Middle Miocene (25 - 13.5 million years ago) to explore fossil crocs with special guest Dr Jorgo Ristevski. We hear about the adorable but extinct Trilophosuchus, other fossils from the Riversleigh World Heritage Site, as well as Quinkana. Plus a tangent on Gunggamarandu aka the river boss and largest extinct croc ever discovered in Australia 

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Today on the show we're talking to our new pal, Dr Jorgo Ristevski. This episode we get inside the head of an ancient animal and talk brain endocasts, discuss the adorable but extinct mekosuchian croc species, Trilophosuchus and pivoting from archaeology to palaeontology.

Pals in Palaeo presents Trilophosuchus with Jorgo Ristevski

I'd like to acknowledge the Traditional Custodians of the land throughout Australia, in particular the Waanyi People, and recognise their connections to land, sky and community. Pals in Palaeo pays our respects to the Elders past, present and emerging, and extends that respect to all Aboriginal and Torres Strait Islander peoples today. This episode was recorded on Koa country, in Winton, central western Queensland, and fossils of Trilophosuchus were found on Boodjamulla Country, in north Queensland.

This is Pals in Palaeo, the show where we talk to real down to earth palaeontologists, and hear about some truly spectacular fossils and extinct animals. 

I'm your host, palaeontologist, PhD student and just, jack of all trades, Adele Pentland. You can stay up to date with the show by following me on Instagram @palsinpalaeo, and that's all, one word. 

Very excited to be talking today about Trilophosuchus which is an ancient species of now extinct croc, with Dr Jorgo Ristevski who I met during fieldwork in Winton on one of the Australian Age of Dinosaurs, dinosaurs digs. 

He was super helpful in the field and just happy to jump in and lend a hand with whatever was going on. And yeah I asked Jorgo on... I think it was Friday night if he wanted to be on the podcast and we got to record this the next day. I'm so glad we did, even though yes it was kind of late by the time we finished recording and we were both a little bit wrecked, a little bir tired after a full day on-site but I learned heaps about fossil crocs and Riversleigh as well which is a super prolific fossil site here in Australia 

Before we hear from Jorgo, who by the way, you are going to love, I've got a couple announcements. First up, if you want to support the show, grab a couple stickers from our online store, they're waterproof and perfect for laptops and water bottles. It helps support the show and also helps spread the word. The other announcement is that transcripts of each episode can be found online. I double check the spelling of all the scientific words and terms and if you're keen to learn more about a topic but don't know where to start, check out the episode transcripts.

Last thing before we launch into the interview, I've gotta tell you about this Random Fossil Fact. As the name suggests it doesn't really relate to the rest of the episode, it's just some cool extra info I wanted to slide into the episode. So as I touched on before, we talk a little bit about the Riversleigh fossil site in this episode, because it's where Trilophosuchus was found but it's a UNESCO world heritage site along with the Naracoorte Caves. They're jointly known as the Australian Fossil Mammal Sites and were given world heritage protection in 1994. 

Anyway, I was kind of curious and wanted to know more about the number of species that have been found. Specifically I wanted to give you the bat, um I mean, give me the bat Marge, uh sorry, the facts on bats. 

We haven't talked about bats before on the show, and can I just say that fossils of anything that can fly is normally pretty rare in the fossil record. Bats by the way are the most recent group, so the newest group of vertebrates, the new kids on the block to develop powered flight, and the only other two groups that have been actually able to properly fly are birds and pterosaurs. 

Bats, birds and pterosaurs all have really thin delicate bones that easily get broken, which is why they're so hard to find in the fossil record.

But! As of this recording, there's been a whopping 35 species of fossil bat recorded from Riversleigh. Which is an absurd number of bats to be dealing with. I mean, it almost sounds like it's Halloween year round there at that one locality. 

By the way this information is pulled from the Australian Museum website, which I highly recommend you check out.

And I also found out that from the 250 plus sites scattered across Riversleigh, there's been hundreds of new species described from the thousands of well-preserved specimens.

As we'll touch on later in this episode, a bunch of other animals have been found from Riversleigh, including the star of the show Trilophosuchus. And without further ado, let's hear more about this adorable croc from the man of the hour, Dr Jorgo Ristevski 

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Adele Pentland (05:24.994)

Adele: Today on the show we have a really special guest. I have once again snuck into the Australian Age of Dinosaur's work ute and I have a really special guest with me, Dr. Jorgo Ristevski. 

Jorgo: Pleasure to be here and thank you for the invitation. 

A: No worries, I'm so spoiled because I get to talk to an expert on a fossil animal that I really don't know that much about or a group of animals that I don't know that much about. How did you get into palaeontology and what are your interests? 

J: Well, my palaeontology journey, you can say it started when I was a toddler essentially. I've always been interested in animals in general, but specifically extinct ones. I was born in the early 90s and 1993 is the big year where Jurassic Park came out. 

A: Wait, you were born in 93? 

J: 91. 

A: Oh, okay. I was born in 93. 

J: Yeah, but you know Jurassic Park came at a time where I was super impressionable with a lot of the media. And, I know it’s kind of cliché at this point where a lot of palaeontologists born in the 80s or 90s have been inspired by Jurassic Park and… Guilty as charged, I’m one of those people as well. 

A: Yeah. 

J: So yeah, I guess my interest in animals in the natural world and all these awesome media like Jurassic Park, Walking with Dinosaurs a few years after Jurassic Park came out, all of that kind of inspired me to pursue a career in palaeontology and it wasn't really certain for a very long time. So I didn't have many chances as a kid in my home country to pursue palaeontology and so...

A:  And is that Macedonia? 

J: North Macedonia, yes. There weren't many opportunities to pursue an undergraduate degree in palaeontology in Macedonia, so I was kind of thinking after I finished high school, well, what next? What do I do? And the best thing, the closest thing that I could probably find was archaeology.

J: And so I've completed an undergrad degree in archaeology in my home country, but after I finished that, my desire to be a palaeontologist just didn't disappear. So my next step was like, “Well, how do I make my dream a reality? How do I become a palaeontologist? Am I just too far gone in a direction that's just not favourable to become a palaeontologist at this point?” But I thought I'd try anyway, so I contacted a few universities abroad to...

(07:33.942)

J: ask, “Hey, I would like to do a master's degree in palaeontology. Is that a possibility considering I have an undergrad degree in archaeology?”, and fortunately the University of Southampton agreed. So I went to England, did an undergrad degree in palaeontology and finished it with flying colours, if I can say so. And then I came to Australia to do a PhD in palaeontology as well and the rest is history. 

A: Yeah, so where did you do your PhD in Australia? 

J: I did it at the University of Queensland in Brisbane. My supervisors were Dr. Steven Salisbury and Dr. Gilbert Price. And I specifically came to Australia to study extinct crocodiles from this continent. So I've been fascinated by crocodilians for a long time. And there were a lot of unknowns about the extinct crocs from Australia. There was a great opportunity to do a bunch of studies on them. And I thought, well, here's an opening. I'm going to seize the opportunity and try to do a PhD on the subject. And so I did. 

A: Yeah. So you saw that there was a gap in our knowledge and that's what you wanted to pursue. 

J: Yep, I've been interested in these extinct crocs which we'll talk about later for quite a while and that's why I decided, well, there's certainly gaps in the knowledge of these crocs and there's certainly plenty left to do and yeah, I just contacted the University of Queensland, particularly Dr. Steven Salisbury about an opportunity to be a PhD student of his and study these crocs and he agreed and I got here to do a PhD in Australia. 

A: Yep, and you finished that as well. Congratulations on being conferred as a doctor. 

J: Yes, thank you. 

A: It's really interesting to hear, you know, you say that we don't know that much about extinct crocodiles in Australia, because I feel like we're so familiar with crocodiles, particularly if you sort of live in North Australia, where there's sort of more contact between people and crocs. 

J: Yeah. 

(09:27.842)

A: But crocodiles have a very long evolutionary history. 

J: Oh, it's mind-boggling and long. So if we go to the very beginning of croc evolution, that would be sometime in the Triassic, like over 200 million years ago. And there have been a bunch of very interesting lineages of crocs that branched out since the Triassic. Some of them have evolved to live semi-aquatic lifestyles, including the crocs that we have today on our planet. And by semi-aquatic, I mean, they live at the land water interface. That's basically their favourite place to live. 

They depend on water for hunting, thermoregulation, protection, reproduction. They do venture on land, they're not fully aquatic, obviously. And some species of living crocs are comparatively more terrestrial or comparatively more aquatic than others. But in the past, some crocs were not just semi-aquatic, some were largely terrestrial. They lived their lives primarily on land and some even evolved flippers and fluke tails, basically croc dolphins, for lack of a better term. 

A: Oh my gosh.

J: Yes, like fully marine crocodiles. And yeah, fascinating mind-boggling diversity of crocs all over the world. We have croc fossils found on every single continent except Antarctica. There is a report of croc fossils from Antarctica, but it's a bit uncertain if those are indeed croc fossils or they are misidentified. But-

A: Surely it’s a matter of time. If they're everywhere else, you know-

J: Yes, exactly.

A: Surely they'd be there if you looked in the right age rock.

J: It makes sense because Antarctica has been fairly warm and lush and green for the majority of Earth's history, especially in the Mesozoic and a decent chunk of the beginning of the Cenozoic era as well. So it would make sense that crocodiles would have made it to Antarctica as well. As you said, it's just a matter of time until we find some really solid proof that they were there. 

A: Yeah, we need the hard evidence. 

J: Yeah, the hard, undeniable evidence. There is some indications today, but it's not like the smoking gun of crocs in Antarctica.

A: Yeah.

J: But in all other continents there have been croc fossils found. 

A: I've also heard crocs essentially occupied every single niche you can think of except for flying. They didn't conquer that but I've heard and correct me if I'm wrong, there were crocs that could climb in trees. Is that right? Or is that an exaggeration? 

J: At this point I would say it's an exaggeration. 

A: OK.

J: So climbing trees, let's kind of unpack that. What would climbing trees mean? 

(11:45.518)

A: OK.

J: So living crocs can and do climb trees on occasion. But in most cases, with some rare exceptions, those climbing of trees is a fallen branch or a fallen log or a semi vertical branch or a semi vertical tree trunk. Something that it's fairly easy to climb upon, right? 

A: Not a koala going straight up. 

J: Yes, exactly. So we wouldn't call living crocs arboreal or tree living. Just like many humans can climb trees, for example, humans are not arboreal. So by that definition then, crocs are not arboreal and we don't have evidence of any extinct croc for being fully arboreal. 

A: OK.

J: And I say we have no evidence, again evidence like that may come up in the future, but at present there is no hard evidence that any living croc was truly arboreal like we would think of a squirrel or a koala or anything like that.

A: OK, thanks for clearing that up because I have sort of been thinking about this and I heard it, you know, from someone else years ago. 

J: Yeah, so that's a myth at this point and again, it could be a fact at some point, maybe, maybe not, but at this point, tree-living crocs is a myth. 

A: Okay, but one fossil can completely change everything. 

J: Exactly. 

A: I don't think we touched on before, so you finished your PhD. Are you currently affiliated with any institution at all?

J: Yes, I'm an honorary fellow at the University of Queensland and I'm a research assistant at the James Cook University as well. 

A: And continuing your work on crocs or are you branching out as well? 

J: For now, what is like six months out of my PhD, I'm still continuing to work on crocs but I have very broad interest in prehistoric animals so I wouldn't mind in the slightest if I do branch out to work on other groups. But I do love my crocs and for now I'm sticking with research on them.

A: And we're going to talk about a really special croc in particular today, Trilophosuchus. When was Trilophosuchus named as a species? Did you get to name it or was it already something that someone else had defined as a species of croc? 

J: No, I did not get to name it. So Trilophosuchus was the fossil that serves as the holotype was discovered in 1985, I believe, certainly in the 1980s.

(13:50.266)

J: In this fossil deposits at Riversleigh. So Riversleigh, by the way, for listeners that may not be familiar, is a famous fossil locality in Australia and in fact it's considered a world heritage area. It has exceptionally preserved fossils from the Cenozoic era, which is by the way the Cenozoic era is the era we are currently living in and Trilophosuchus was discovered as I said in the 1980s and it was officially named in 1993 by Dr. Paul Willis. Shout out to Paul, he is one of the, it's safe to say the godfathers of Australian croc palaeontology. He is truly a legend in this field. So I didn't get to name the species, I was basically a toddler when it was named, but... For my PhD research, I think it's okay if I say half of my PhD thesis was focused on Trilophosuchus. So what I did on this animal was study the fossils in far greater details than what was possible some 30 years ago. I seized the advantage of modern technology, particularly CT scanning, to have the specimen scanned and examined its anatomy to a previously unprecedented detail. 

A: So CT scan being... not too dissimilar to an x-ray looking at the internal structure and I guess being able to pinpoint more precisely things that we can't just see by looking at the fossil as if we were holding it in our hands. 

J: Exactly. So... we're really literally looking inside the bones of the skull of this animal. And CT or computed tomography is something that is fairly accessible in hospitals, so it's used to treat or diagnose rather patients. So it's not some elusive or rare technology, but its application in palaeontology is relatively recent. It has become a mainstream or a common tool in palaeontology in the past 10-15 years. So it's a fairly recent thing that palaeontologists have been utilizing CT scanning to such degree in the grand scheme of things.

(15:37.744)

A: Yeah, so I've actually had some stuff CT scanned at a hospital, which was very interesting. But some other universities as well have their own CT scanners, is that fair to say? 

J: Some do, yes. Like the University of Queensland, which is where I scanned the specimen in question of Trilophosuchus. The holotype.

A: So to zoom out, how old is Trilophosuchus? 

J: So there is only one species of Trilophosuchus. So Trilophosuchus is the genus and Trilophosuchus literally translates as three crested crocodile. And the reason for the name is the presence of three longitudinal crests on the top of the animal's skull. 

A: So with longitudinal… 

J: So back to front, back to front on the top of the skull. 

A: Yep.

J: It's got three distinctive crests which are quite unlike any other croc. They really stand out among other crocs when you see them visually. So there is one species within the genus Trilophosuchus, Trilophosuchus rackhami, and rackhami, the name of the species, is in honour of Alan Rackham, who is one of the people that worked at the Riversleigh World Heritage Area and helped with the discovery of fossils over there. So the species Trilophosuchus rackhami is approximately 13.5 million years old during a period of time that we call the middle Miocene. 

However... there is evidence of the genus Trilophosuchus, but it's uncertain if this is the same species as Trilophosuchus rackhami. But evidence of the genus Trilophosuchus from the late Oligocene, approximately 25 million years ago. 

A: Oh, okay. 

J: So that's something that we found out fairly recently and that indicates that the genus Trilophosuchus is about 10 million years older than what was thought previously. 

A: That's, that's a... pretty significant shift. 

J: Yeah, yeah. We basically shifted the known presence of these genus by 10 million years, which is a huge time leap. 

A: Yeah, that's incredible. 

J: Yes. 

A: So it's fair to say most people probably know what a croc is. As we touched on before, there's a lot of diversity in the roles that they played within their environment, and I'm assuming their bodies changed a lot as well. Some were quite large and then others were small. Where does Trilophosuchus fit in terms of other crocs? Is it quite big? Is it small?

(17:44.566)

J: That's a great question and the answer is quite easy. It was pretty small for a croc. In fact, based on the holotype specimen, and we do have a few additional quite fragmentary specimens to kind of back this up, is that Trilophosuchus was quite small for a croc, and the estimated size of the holotype was between 70 to 90 centimetres head to tail. And that's at maturity. So... Less than a meter long. 

A: Less than a meter long, so that would be about... three feet and a bit?

J: Oh, I'm a bit rusty with feet. 

A: I'm also rusty with feet. Sorry, US listeners. 

J: Yeah, really sorry. 

A: Open up Google and do your conversion, but it's not that big. I reckon it would make a pretty good house pet. If you could train it. 

J: Yeah, well, if it was anything in its behaviour like modern crocs, it would be really not friendly. So it wouldn't be able to eat you, like most crocs that we have today, but you’d probably lose a finger or two if you tried to bother it too much. I wouldn't have it as a pet. I mean, it would have been adorable, but I don't think it would like being a pet. 

A: Okay, that's fair enough. You mentioned before the three distinctive crests. Is that one of the features that was used to define the species and are there others? 

J: That was one of the features that were used to define species, yes. There are multiple other features in the skull that we consider autapomorphies or diagnostic features. 

A: With the holotype, that bones do we have in the holotype specimen? So we've talked about the skull. 

J: So the holotype is an exceptionally well-preserved skull that is missing the snout. So we are missing off the top of my head like four or five bones in total. 

A: That's pretty near complete. 

J: Pretty near complete and again the preservation is phenomenal. It's as if the animal died yesterday essentially. There is no matrix or any soil residue which is quite common in fossils. 

A: Is Riversleigh, a cave deposit?

J: It is often referred as a Lagerstätte and now whether this specimen was deposited in a cave some 13 million years ago, I am not sure and I think there's not much of a consensus in regards to this question so I'm not sure if anyone can answer this with confidence at this point I could be mistaken so…

(19:59.538)

A: Okay. 

J: Yes. 

A: But yeah, a Lagerstätten is a German word and it essentially just means, uh, there's a direct translation that I don't know because I didn't study German, but essentially it just means there's a treasure trove of incredible fossils. You know, often it's, you know, hundreds, I guess, if not thousands of specimens that are just incredible. 

J: Yeah, Riversleigh is rightfully considered a World Heritage Site, and it's renowned for its phenomenally preserved fossils, not Trilophosuchus, but a bunch of marsupials and other reptiles. 

A: Bats as well. 

J: Bats, yes. 

A: Multiple species of bats. 

J: Birds, lizards, I mean, you name it. 

A: Snakes.

J: Snakes, monotremes, yes. 

A: Yeah, so it gives you a brilliant snapshot of what is in the environment. Were there other crocs sort of present as well or was it just Trilophosuchus? 

J: Yeah, we do have evidence of other crocs from the same deposit or site at Riversleigh. So there are multiple fossil sites at Riversleigh. So the site that Trilophosuchus comes from is called the Ringtail site and from the Ringtail site we have evidence of other crocs like pretty large species of Baru, which is another extinct croc from Australia.

J: And interestingly, we have evidence of another species of pretty small-bodied croc similar to Trilophosuchus called Mekosuchus sanderi. 

A: Okay, that's really interesting that you have two very similarly sized crocs, presumably living in the same environment at the same time. I mean, the bigger one kind of makes sense to me in that, well, they're probably chasing different prey. 

J: Yeah, exactly.

A: But we might be able to see differences in the teeth. Were teeth found with Trilophosuchus?

J: Unfortunately, not we do not have any teeth for Trilophosuchus.

A: And yeah, if there were replacement teeth coming through the jaw you would have seen that in CT scans…

J: I would have, no the teeth socket are completely empty in the fossil unfortunately. Not a trace of a tooth sadly. 

(21:52.13)

A: Well still I'm guessing you're able to determine a lot more about this animal just based on the brain endocast. So studying where the brain sat in the skull. I will say before we recorded, I got to see a 3D print of it and it's incredible. It's incredibly detailed. So we sort of talked a little bit about the form of Trilophosuchus in terms of its function and how it played its role within its environment. Where do you see Trilophosuchus within Australia 13.5 million years ago? 

J: Well, the Ringtail sites where Trilophosuchus was found from, the holotype at least of this genus, is inferred to have been like a foresty or rainforest environment. So based on that we can probably assume that Trilophosuchus liked its forests. As to its palaeoecology… 

Now, we can only make educated guesses and inferences based on its anatomy at this point. So, of course, future studies may very well prove that something else happened with Trilophosuchus as far as its lifestyle. But at this point, the major hypothesis, the leading hypothesis is that Trilophosuchus was largely, maybe not exclusively, but largely a terrestrial crocodilian. Probably more so than what we see in living crocs today. 

Now, the reason why we think Trilophosuchus might have been more terrestrial than most living crocs, which are again semi-aquatic, comes from some of the features in its skull as well as its brain case. So inside the skull features that we could not see by just looking at the actual fossil itself, but through CT scan data. 

And also another thing that may... support further the hypothesis that Trilophosuchus may have been more terrestrial is its position in the family tree of crocs. It is really closely related to some other extinct crocs from Australia that are also strong contenders for being terrestrial crocs. So when you combine all those features together, a terrestrial palaeoecology for Trilophosuchus seems to be the most likely. 

A: So it's not an ambush predator hanging in waters the way we see modern crocs today. In terms of studying brain case, which I probably should have mentioned with form. What is it like to study what is essentially a fossil brain?

Adele Pentland (24:00.526)

J: It is pretty exciting when you get the CD data. It's unprocessed, it's raw, like the brain and the cast or any other features inside the skull. The scientists has to reconstruct them themselves. 

A: So the raw data just to zoom out… I've heard an analogy from a friend saying it's like seeing multiple slices through a 3D object and then you need to put them together. 

J: That's a fairly good analogy. Yes. So basically when you get the CD data, you then open it and manipulate it in specialized software. There's multiple such programs and it's really up to the preference of the scientist, which one they're going to work with and availability of course. 

A: Cost is a big factor. 

J: Yes, cost is a huge factor. Some of these programs cost thousands and thousands of dollars a year. It's not like a one and done payment. You have to pay each year to keep the license. 

A: That's how they get you. That’s how they make their business. 

J: Yeah, exactly. So fortunately universities and grants do cover those costs in a lot of cases because you really can't pay out of your own pocket unless you're a millionaire. Yeah. So... 

A: I don't know too many millionaire palaeontologists either. 

J: Nope. If you do know... by any chance, just let me know. I'd love to meet them. 

A: Yeah. 

J: But yeah, once you process that CD data in a specialized software, you reconstruct the cavities of interest. In this case, let's say the brain cavity and the inner ears and some of the sinuses or air spaces in the skull, if you will. And voila, you have reconstructed the brain case of this animal. And it's pretty exciting when you see it for the first time, because the exciting part for me at least is that you are the very first human being that has ever seen this structure. And by the way, again, this is not something that you can observe by looking at a fossil. This has to be done through elaborate methods like CT scanning to get it. You can't just look at the fossil and say, oh, this is the shape of the brain endocast. So that being the very first person to know this, to see this, it's really exhilarating in my opinion, at least. 

A: Is it surprising to look at it? So in terms of doing this work on Trilophosuchus, did you look at... brain endocasts in modern crocs to see how developed the sense of smell is, the olfactory, or how keen the eyesight is. Did you do any of that?

(26:14.198)

J: No, I didn't do any analysis like that. There were some issues with the completeness of the specimen in particular areas, like the sense of smell, called the olfactory bulb. They could not be reconstructed completely in the holotype of Trilophosuchus, because at that part where those structures would be are slightly damaged.

J: So it would not have been a reliable estimate based on what the specimen allows to figure out. But I certainly did compare the overall morphology of the brain endocast of Trilophosuchus to living crocs and to data of other extinct crocs. Well, as many as we had available at the time of the study, of course. By the way, palaeoneurology is the field of study that... focuses on studying the nervous system in the brain of extinct animals, and crocodilian palaeoneurology is an ever-evolving field. There are literally multiple papers every year published on that topic. So we get new data every year, and I think it's going to just go faster and faster with each passing year, as CT data and CT scanning technology and these specialized software become more available and widespread among scientists. 

A: Yeah, and the incredible thing is that this... work can be done using fossils that have already been collected from years and years ago. 

J: Yes, exactly. You can always kind of revisit a fossil, apply the latest technology to it, and do a completely new type of study, learn completely new things that were not possible to learn 30, 50, 100 years ago when it was originally discovered, which is really amazing. Like, I'm just excited to think like 50 years from now will someone else do a study in Trilophosuchus and what will they find out with the new technology at that time? I'm just looking forward to that.

A: I mean, well, it could be you again. Maybe you'll revisit this fossil. 

J: Maybe, we'll see. I never say never. 

A: Or you could be supervising them. That would be pretty cool if you want to teach. 

J: We'll see. Yeah, the future is unknown at this point. We'll see what happens. 

A: So in terms of the family grouping of Trilophosuchus, is it closely related to some of the modern day crocs that we have in Australia, or is it more closely related to other crocs from that time period?

(28:27.514)

J: So, Trilophosuchus belongs to this group of crocodilians that we call the Mekosuchinae, or just Mekosuchines. Makosukines, in my opinion, are a fascinating group of crocodiles that are sadly all extinct. They were widespread in Australia for the vast majority of the Cenozoic. The earliest known Mekosuchine, it's called Kambara, that's the name of the genus, and it is known from the Eocene epoch, so roughly 50-ish million years ago.

And there were a bunch of mekosuchines that lived in Australia. And the last known mekosuchines died out during the last ice age. So approximately 50,000 years ago or something like that. Trilophosuchus obviously as I said before lived about 13.5 million years ago. That is the most recent evidence of Trilophosuchus. The earliest being some 25 million years ago. 

But mekosuchines didn't live just in Australia. They also lived in some South Pacific islands. Like we have evidence of mekosuchines from New Caledonia, Vanuatu and Fiji. They're possibly present on New Guinea as well. And there is some evidence which is not super robust at the moment. We'll see how it holds up in the future, but maybe they actually originated in Asia. 

A: Okay. 

J: But again, the Asian origins of Mekosuchines is a fairly novel hypothesis at this point, and it needs further testing. So... We'll see how well it holds up or not in the future. But Mekosuchines were absolutely present in Australia. They were the dominant croc group during the Cenozoic and in my opinion they're fascinating. Not only because they were so successful for so long, but they evolved a variety of body sizes and trophic niches. Australosuchus was most likely a terrestrial croc and it was a very small-bodied croc to begin with. There were also other terrestrial crocs like Mekosuchus. 

J: Mekosuchus, by the way, did survive until fairly recently. Most recently it existed on Vanuatu and it went extinct probably some two or 3000 years ago. 

A: In terms of palaeontological timescales, that's just like yesterday. 

J: Yeah, it's barely a blink of an eye in the grand scheme of things. It's pretty disappointing, because…

(30:37.462)

J: we almost...had Mekosuchus alive and breathing today. And Mekosuchus is a very close relative of Trilophosuchus. It also was a small croc, about a meter long on average, and it was most likely land-based, a terrestrial croc. And yeah, it's pretty heartbreaking to know that we could have had Mekosuchus alive and breathing today, and sadly we do not. 

A: This is something that I wanted to talk about earlier in the episode. Crocs have been incredibly... diverse before. There's not that many species around today and it's just a sliver of the diversity that we've seen previously. 

J: Yes, like the diversity of crocs that we have today on the planet, it pales in comparison to what it was in the past. We do have a better under 30 recognized species of crocs today. 

A: Worldwide? 

J: Worldwide, yes. So we have two living in Australia, the freshwater crocodile, which is the only endemic species of crocodile in Australia.

The second species is the saltwater crocodile or estuarine crocodile. In the Pacific crocodile, there's multiple names for this species, which is also the largest reptile on earth today. But it doesn't live only in Australia. It occupies a huge territory in Southeast Asia and South Asia, specifically India. So the saltwater crocodile, it's not endemic to Australia, just a freshwater crocodile. 

A: Yeah, I feel like Aussies often claim them as being an iconic thing but yeah it's good to remember that you know it might be somewhere else too. 

J: Yeah it is an iconic Australian animal but it's not just an Australian animal. 

A: And then there are gharials? 

J: Gharials, yes so today we have just two species of gharials that live in Asia. 

A: They're the ones with the really long... jaws but then like a sort of bulbous at the end. 

J: Yes. So. 

A: Spoonbill crocs. 

J: Yeah, kind of. So the gharials are characterized by their relatively thin and very long snouts with sharp needle-like teeth which are pretty good for catching fish. Now the bulbous thing that you mentioned that is called a ghara and it is a soft tissue structure that is sexually dimorphic and sexually dimorphic means it occurs only in one sex of that species. So the ghara and the gharial occurs only in males.

(32:42.622)

J: The ghara itself is not fossilized because it's soft tissue, it doesn't have any bones in it. It occurs in the very tip of the snout around the nostrils. But when you look at the snout of a ghara like the skull, the dry skull, you can kind of make out where that soft tissue structure would have sat at the tip of the snout essentially. And fun fact, we did have gharials in Australia that lived quite a long time ago.

J: One comes from the Northern Territory, it's called Harpacochampsa. It lived about 15-ish million years ago, give or take a couple of weeks. And the second one is called Gunggamarandu, which is known from Queensland. And Gunggamarandu is one of the largest and maybe the largest croc that we know from Australia ever at this point. Of course, future discoveries can certainly change that. But at the moment Gunggamarandu is the strongest contender for the largest croc from Australia. 

It's... Probably clocked at seven meters easily, maybe a bit over that. 

A: That's pretty massive. 

J: Yeah, pretty massive. Pretty massive, yes. 

J: Hey, for those who aren't familiar with the metric system, seven meters is just shy of 23 feet long. So this was an absolute unit. You would not want to mess with this giant extinct croc. Okay, back to your go and the interview. 

J: But again, mekosuchines, like Trilophosuchus, are not part of the gharial family group. There is a bit of contention where exactly mekosuchines fit in the croc family tree. The most known hypothesis that they are closely related to Crocodylidae or the group that includes the modern crocodiles and some of their extinct relatives. But there is a second hypothesis that suggests that they are more basal to crocodylids. So in this hypothesis, the gharials and crocodiles...

The Gavialidae or Crocodylidae to be a bit more technical would be fairly closely related clades and then we have the mekosuchines outside of that clade and then situated kind of more basal to the mekosuchines plus gharials plus crocodiles would be the alligators and caimans and their relatives and of course this is a super duper simplified version of the relationships there are a bunch of other extinct crocs that kind of go in between and around all this, but for the purposes of providing a very simplified relationship of mekosuchines, when we take into consideration the living crocs only, those are the two main hypotheses as to where mekosuchines would fit.

(34:57.602)

A: Okay, so mekosuchines, did they have like a defined head shape or they just did everything? 

J: They did a bunch of things. So we have some mekosuchines that looked like quote unquote fairly generic crocs. So for example, Kambara or Australosuchus are just two Mekosuchine genera that come to mind that had moderately big sizes, three-ish, four-ish meters, which it's not a small line of any means, but it's nothing exceptional for a croc. They also had flat and kind of squished or low snouts, kind of like what we see in crocodiles and alligators today. 

Some were quite large, like species of Baru or species of Paludirex, which could grow to five plus meters in length. They also had relative to flat snouts, particularly Paludirex, and they were built for taking down very large prey animals that lived in their environments at the time. Then of course we have Trilophosuchus and Mekosuchus, which were quote unquote dwarfs, basically the adorable mekosuchines. And then we have something really cool in my opinion, which are the tall-snouted Ziphodont crocs, specifically the genus Quinkana. 

A: Ziphodont, that... has something to do with the teeth? 

J: Yes, correct. So the term ziphodont literally translates as knife teeth. So ziphodont tooth is basically fairly flat and has serrations along its edges, kind of like a steak knife. So for example, modern crocs tend to have conical teeth without serrations. These teeth are pretty good for grabbing onto prey and then holding it and then dragging it underwater to drown it and eat it. 

A: Or doing the death roll. 

J: The death roll, yes. But serrated teeth or ziphodont teeth, like those of Quinkana are good for slicing through flesh. Kind of like a Komodo dragon or theropod dinosaurs. 

A: Yeah, okay, wow. So in terms of sort of hunting strategies, were you able to make any... hypotheses or guesses about what the hunting style was for Trilophosuchus?

(37:03.682)

J: Unfortunately not, and one of the reasons why we couldn't figure that out is because we didn't have anything of the post-cranial skeleton of Trilophosuchus, so we didn't know what the limb bones were like for this animal. 

We also don't know what the teeth were like, as I said before, but as far as its palaeoecology goes, I did mention before why we think it was terrestrial, and to be a bit more specific, there are certain features in the skull, like the oral shape of the skull is kind of box-like and the snout is indicative to being quite tall, so not flats and broad like we see in extant crocs or living crocs or unlike the gharials which have very thin snouts. 

Trilophosuchus would have had a relatively short and rather tall or trapezoid-like snout in cross-section and a fairly tall brain case, like a squarish brain case. 

And then within the brain case when we look at this neuroanatomy we found out that Trilophosuchus had very well developed pneumatic sinuses or pneumatic spaces inside the head and that pneumatic development within the skull of Trilophosuchus is not identical but most similar to that seen in some other extinct crocs from the Mesozoic and some crocs from the Cenozoic era from across the world that are also thought to have been terrestrial and that degree of pneumatic development is a bit greater than what we see in living crocs which are semi-aquatic. 

So when we have a look at those anatomical features in Trilophosuchus, we get an indication that this animal probably spent a bit more time on land than your average croc does today. 

A: I might be misunderstanding this. How is it, the pneumatic? 

J: Pneumatic structures. 

A: That's not related to like the nasal cavity, that's different. 

J: No, so crocs have a lot of hollow spaces, generally speaking, in the skull. And what we see in fossil crocodilians, like for example the thalattosuchians or the quote-unquote dolphin crocs that I mentioned earlier in the talk, have extremely reduced pneumatic structures in the head, comparatively speaking. 

And then semi-aquatic crocs like the ones that live on the planet today have more developed pneumatic structures and then more terrestrial crocs from the known fossil record have more developed pneumatic structures compared to living crocs and significantly more pneumatic structures than... these fully aquatic thalattosuchians.

(39:21.27)

J: And Trilophosuchus, comparatively speaking, has pneumatic structures that are more closely resembling the development of those seen in these terrestrial crocs than the semi-aquatic or the fully aquatic crocs. 

A: Okay, so with the pneumatic, with the air spaces, it's often the case that marine animals don't have a lot of that. So marine animals will often have really dense bone, but then they'll regulate where they are in the water column by using sometimes organs or things like that kind of tie in? 

J: Potentially. In crocodilians this is still a topic that has been actively researched on so we can't really say for sure but yes in general as you said Adele like aquatic animals do tend to have denser bones with less pneumatic spaces in them which helps them stay in the water more easily so they don't float as easily to the surface so they can stay underwater more effortlessly so to speak.

A: Before we wrap up, I love to touch on pop culture references where this animal has made an impact. If it was maybe featured in walking with dinosaurs and things like that. Are there any like, Trilophosuchus figurines that you have in your office? I know a bunch of palaeos, the group that they work on. If they can get their hands on them, they'll have little replicas, maybe 3D prints of what they work on as well. Is that kind of what your office used to look like? 

J: Yes, well with one small caveat, unfortunately there aren't many figurines of mekosuchines. There are only two mekosuchines that have been made into toys slash figurines, Quinkana and fortunately Trilophosuchus, which I'm a proud owner of two Trilophosuchus figurines. So they were produced I think in the early 2000s by Yowie. 

Now for international listeners... that may not know what a Yowie is. If you're familiar with Kinder Surprise Eggs, Yowies are pretty much the Australian exclusive version of that and they usually have some animal figurines inside them, like it's a chocolate egg essentially with a plastic toy as a bonus in the middle of it. And back in the early 2000s, there was a promotion of a Yowie toy it's called Lost Creatures or something like that.

A: I think Lost Kingdom? 

J: Lost Kingdom, yes, I think that's the one. And there were a bunch of extinct animals from Australia that... were made into figurines and one of them was Trilophosuchus.

(41:40.214)

J: The other one that was also made into a figurine that are mekosuchine is Quinkana. And to the best of my knowledge, I'm afraid those two are the only ones that have made it into the figure realm. If any toy manufacturer is listening to this podcast, please make more mekosuchine toys, especially Trilophosuchus because it's adorable. Thank you very much. 

A: It's like a dream of mine to get onto Yowie and say, you could easily make just do Lost Kingdom version 2. Like there's been so many amazing fossils that have been found since that first-

J: I think it's a no-brainer. 

A: I mean there are heaps of people our age that would love it and kids would love it too. 

J: Yeah exactly. I mean kids would love to play with them and people like us palaeontologists would just love to decorate their office space with the animals that are working on. 

A: Yeah and the great thing about Yowie as well is that there's normally like a slip of paper like a little stat sheet when they used to come in multiple pieces that you assembled together there was the instructions on how to put it together and then also a little bit about that animal so you got to learn about that.

J: Yeah that's what accompanied the Trilophosuchus figurine, a little sheet of paper that was like popular facts about it. I don't have it with me so I don't remember what it said or how accurate it was but it definitely came with a little fact piece quote-unquote fact back in the day and you know what for a the anatomical accuracy of the Trilophosuchus Yowie is not too bad. I mean, it's far from the most accurate figurine ever made, but considering what it is, it's not the worst either, that's what I'm gonna say. 

A: Yeah, the figurines, they're only about like an inch or like three or four centimetres. 

J: Pretty small, I mean, something that you can fit in a chocolate egg, really. 

A: Yeah, exactly. 

J: So, Kinder Surprise is a pretty good analogy to what Yowies are for international listeners, especially in Europe and Asia. If you know what a Kinder Surprise egg is, YOW is basically that, essentially. Yes. 

A: We'll leave it there. It's 9.30 at night. We have been chatting for close to an hour. And it's been a long week. You've put in more hours this week than I have. 

J: Yes. 

A: I hope you enjoyed. How did you find your first Australian-aged dinosaur's dinosaur dig? Or have you done a lot of field work before? 

J: I have done some field work, particularly in Europe. I've done field work in the UK, in Portugal.

(44:02.114)

A: With your previous degree, your first degree? 

J: Yeah, and my master's degree, yes. But in Australia, I have done some prospecting, like our basically daily field trips in Australia before, but nothing in Australia at least to this degree like I've done this past week with the Australian Age of Dinosaurs Museum. Had a fantastic time and I really hope to come back and do some more field work next year.

A: Yeah, well, it would be awesome. Hopefully we'll see you then maybe I'll bail you up in the work you'd again and we'll chat about another fossil croc. Otherwise I might see you later in the year at CAVEPS, but yeah, we'll see how we go. 

J: Yeah. I hope to make it to CAVEPS. Yeah. 

A: Well, thank you so much for being so generous with your time. 

J: Thank you for having me on the podcast. It's, it's an honour and a pleasure.

Adele Pentland (44:52.706)

A: What a top bloke. I hope you enjoyed hearing from Jorgo about his work on Trilophosuchus and using bones to study brains. I could have talked to him for hours if I wasn't so bloody tired from the dig. Thanks heaps for listening to pals in Palaeo and hanging out with us. I hope each episode feels like, yeah, just chilling and hearing about what it's like to actually study fossils and stuff.

A: The podcast cover art is from the talented Jenny Zhao, a freelance creative and co-founder of Crumpet Clubhouse. You can find their work on Instagram @jennyzdesign and @crumpetclubhouse. Our theme music is by Canadian pop rock outfit, Hello Kelly. And you can find them on Instagram at Hello Kelly Music. And you can also find their latest album, Sweet Nostalgia on Spotify, Apple, and anywhere you get good music.

A: Final thank you goes out to our podcast editor, Francie for making the podcast sound super squeaky clean. The audio that I send him raw does not always sound super great, but he works his magic every time. He's an absolute wizard when it comes to sound production and music. And yeah, I'm super grateful to have him on board.

A: I already said this before, but again, thank you so much for listening. You can catch me on Instagram at pals and palaeo. I'll be hanging out there and otherwise until next time, keep digging, keep cool and keep hydrated.


References

Riversleigh

Fossils in Riversleigh, QLD
https://australian.museum/learn/australia-over-time/fossils/sites/riversleigh/

Australian Fossil Mammal Site – Riversleigh section, World Heritage Area
https://parks.des.qld.gov.au/management/managed-areas/world-heritage-areas/current/riversleigh

Trilophosuchus

Trilophosuchus rackhami

https://australian.museum/learn/australia-over-time/extinct-animals/trilophosuchus-rackhami/

Scientists tap into mind of 'most adorable' Trilophosuchus rackhami crocodile

https://www.abc.net.au/news/2022-08-30/scientists-research-tiny-crocodile-trilophosuchus-rackhami/101382078

Cranial anatomy of the mekosuchine crocodylian Trilophosuchus rackhami Willis, 1993

https://anatomypubs.onlinelibrary.wiley.com/doi/full/10.1002/ar.25050

Quinkana
https://australian.museum/learn/australia-over-time/extinct-animals/quinkana/

Baru darrowi

https://australian.museum/learn/australia-over-time/extinct-animals/baru-darrowi/

A review of Australia’s fossil crocs

Migrations, diversifications and extinctions: the evolutionary history of crocodyliforms in Australasia

https://www.tandfonline.com/doi/full/10.1080/03115518.2023.2201319