Thursday, March 08, 2018

Theropod Tooth Replicas
















Above are two Spinosaurus tooth replicas, one still in its original packaging. The dentition of spinosaurids converged with that of crocodilians, and suggests piscivory. In contrast to teeth which ripped dinosaurs apart, the conical teeth of spinosaurs just maintained a grip on aquatic prey. Generally Spinosaurus and close relatives waded or swam in estuaries and rivers, hunting fish. Spinosaurs occasionally devoured other, small dinosaurs but were basically not adapted to fighting and hunting on land.

















Carcharodontosaurus (tooth replica above) lived alongside Spinosaurus and the titanosaur Paralititan. It may have killed and eaten both. The serrated, bladelike teeth of Carcharodontosaurus indicate a lifestyle unlike that of spinosaurs and more typical of large theropods i.e. hunter of large terrestrial prey (those which lacked osteoderms, hence could be slashed by sharp teeth).


















Above is a detailed copy of a Giganotosaurus tooth. Giganotosaurus was a giant predator roughly contemporaneous with Carcharodontosaurus. As its dentition indicates, it filled the same predatory niche. With its deadly teeth, Giganotosaurus slaughtered sauropods such as Nopcsaspondylus and Andesaurus.
















This replica indicates further variation in theropod lifestyle or prey preference. The teeth of Tyrannosaurus were more robust than those of carcharodontosaurs. Whereas the latter evolved to slash unarmored prey, Tyrannosaurus teeth evolved to cope with big armored quarry, originally Alamosaurus, but were also effective against ankylosaur armor and ceratopsian defenses (including tough scales).

27 Comments:

Anonymous Neal Robbins said...

Tyrannosaurus was definitely an apex predator. Its dental arsenal was indeed formidable. Tyrannosaurs in general were powerful carnivores, but I would say that T. rex was the champion. Large carnivorous theropods had to go after substantially sized prey in order to adequately feed themselves. So their situation was more critical than that of small theropods such as Troodon and Velociraptor, who did not require as large an amount of meat. Herbivorous theropods like Therizinosaurus did not have to worry about procuring meat.

6:55 AM  
Blogger starman said...

Yes, I think we can assume that the largest theropods evolved to overcome big herbivores, partly by means of dentition which conferred good cutting or penetrating power. T. rex probably needed the latter.
Btw further news and comments about the field trip can go here.

March 8, 2018

7:22 AM  
Blogger starman said...

We're currently locked in a winter weather pattern. Can you believe we'll get more snow on the first day of spring??! But we should get a compensatory warming trend, so March may go out like a lamb. :)

March 17, 2018

5:45 AM  
Blogger starman said...

By the way, I saw Mercury last evening. Seen though 70mm binoculars it looked conspicuous enough. Mercury was then one day past greatest eastern elongation. Venus was brighter and appeared to its lower left, low in the western sky.

March 17, 2018

5:49 AM  
Anonymous Neal Robbins said...


It's warm here in Arkansas. I think that Arkansas will have an early spring. I went outside a few minutes ago and did not have to wear a coat.

8:38 AM  
Anonymous Neal Robbins said...


You're getting some excellent observations of the planets. As we know, Mercury and Venus are the two hottest planets in this solar system.

8:40 AM  
Blogger starman said...

I hope warmer weather finally gets here next week.
Last evening I saw Venus and Mercury again. Mercury was two days past greatest eastern elongation and sinking lower. Soon, it'll disappear from the evening sky. But it should still be visible tonight and tomorrow night.
Have you seen Mercury at any time?

March 18, 2018

2:47 AM  
Anonymous Neal Robbins said...

I have seen Mercury, but it has been a while. It clouded up during the latter part of yesterday afternoon here. I would like to get a telescope. My father had an excellent one; when I was a kid, our whole family looked through it at the planets and various stars. During World War II, my father was in the Marine Corps and took part in the Pacific campaign. He said that he saw some constellations that cannot be seen in the U.S.

5:13 AM  
Blogger starman said...

I saw Venus and Mercury again last evening—the fourth evening in a row I saw them. I used 70mm binoculars. While viewing them, I noticed the very slender crescent moon, below and to the left of Venus.
What kind of telescope would you like to have? Reflectors may give you the most for your money but I like the crisp images of refractors.

March 19, 2018

1:52 AM  
Blogger starman said...

By the way your father probably saw the Southern Cross and stars like Canopus, too far south to be seen here. Did he mention anything specifically?

March 19, 2018

1:54 AM  
Anonymous Neal Robbins said...


Yes, he mentioned the Southern Cross and Canopus. I would like to get a reflector, though I am open to the possibility of purchasing a refractor. I need to look at the prices.

3:09 AM  
Blogger starman said...

Telescopes tend to be pretty expensive, especially the larger ones. Is a 60mm refractor too small for your tastes?
Spring begins officially today but tomorrow we may get snow...

March 20, 2018

1:59 AM  
Anonymous Neal Robbins said...


I would settle for a 60 mm. refractor. It's cool and cloudy today in Arkansas. There is a possibility of rain.

10:08 AM  
Blogger starman said...

I got a 60mm refractor back in late 1973, and it worked well down to the 2004 transit of Venus. But I also ordered a ten inch reflector back then. It was the biggest instrument I ever had. Lately my biggest scope has been a 150mm reflector.
Today the weather will be disastrous. We’re bracing ourselves for another big snowstorm!! What an awful disappointment on the first full day of spring.

March 21, 2018

2:00 AM  
Blogger starman said...

Btw what would you like to see with a 60mm refractor? Someone once said it’ll show anything an amateur would want to see.

March 21, 2018

2:02 AM  
Anonymous Neal Robbins said...

Planets in this solar system, along with the moons of at least some of them. I would also like to get some views of other galaxies, hopefully Andromeda and maybe the Magellanic Clouds. It's partially overcast outside here on the 1st day of spring in Arkansas.

5:52 AM  
Blogger starman said...

So much for the big nor’easter. It was still snowing before dawn but there was virtually no accumulation where it counted. Hooray!! :)
A 60mm telescope will show lunar craters, Jupiter’s moons and Saturn’s rings etc but they look awful tiny. When I see them with my 70mm refractor I use the highest possible magnification (conferred by a 5.1mm eyepiece) but they still look quite small. I am impressed, however, by the crispness of images compared to those in a reflector.

March 22, 2018

1:48 AM  
Anonymous Neal Robbins said...


I've been doing some research on Carboniferous fauna of Arkansas. Arkanserpeton arcuatum was a Carboniferous temnospondyl amphibian. Fossil remains of it were found in the Allegheny Formation (Paris Shale Group) in Logan County, Arkansas. They date to the Kasimovian age (307.0 - 303.7 million years ago), which was the next to last age of the Carboniferous. Arkanserpeton is in the family Dissorophidae. So it is possible that my team will find some temnospondyl remains.

11:06 AM  
Blogger starman said...

Interesting. How big was Arkanserpeton?

March 24, 2018

2:40 AM  
Anonymous Neal Robbins said...

I don't think that Arkanserpeton was very big. I did some research on the members of its family, i.e. Dissorophidae. That group originated in the Carboniferous and lasted into the early Permian. Going on what I've read about them, they were small. Cacops was a member of Dissorphidae; it had a length of about 40 cm. (1.3 ft.). Cacops lived during the Permian. I have not found data on the length of Arkanserpeton, but I doubt that it was large. Fossils of amphibians of the Dissorophidae family have been found in North America and Europe, so they were not as widespread as some other amphibian groups.

5:31 AM  
Blogger starman said...

Maybe your team can find remains clarifying a number of questions, including size. You’ve said you like temnospondyls before, didn’t you?

March 25, 2018

2:02 AM  
Anonymous Neal Robbins said...


I like temnospondyls a lot. They are one of my favorite groups of fossil groups of fossil creatures. Many families of them have been identified. Temnospondyls were among the survivors of the end Permian extinction event. A few even made it into the Cretaceous. Temnospondyls varied in terms of shapes and sizes. I would like to eventually write a book on temnospondyls. I hope that my team can find some temnospondyl fossil remains.

5:29 AM  
Blogger starman said...

Hi Neal. So why did temnospondyls survive the end Permian crisis? When did they disappear entirely? Are there theories on why they survived Siberian Trap volcanism and its effects, and why they disappeared at the K-Pg or earlier?

March 26, 2018

7:04 AM  
Anonymous Neal Robbins said...


Being able to stay submerged in water must have been one of the factors involved with their survival of the end Permian mass extinction event. Animals that could dive or burrow had a better chance of avoiding the toxic substances thrown into the air by volcanic eruptions. Prionosuchus plummeri was a large temnospondyl of the Permian. It grew up to about 3 m. (9.84 feet). Remains of Prionosuchus have been found in the Pedro de Fogo Formation in Brazil. They date to the Kungurian age (283.5 - 272.95 years ago)of the Permian. Temnospondyls had a higher casualty rate in the end Triassic extinction event. Only the Brachyopoids, trematosauroids, and capitosauroids survived that catastrophe. The latest known temnosopondyl is Koolasuchus cleelandi. Fossil remains of it were discovered in the Wonthaggi Formation in Australia. They date to the Aptian age of the Cretaceous. Koolasuchus was definitely a giant; its length was 4-5 m. (13.1-16.4 feet). Fossils of crocodylomorphs have been unearthed in the region. Competition from crocodylomorphs may have caused the extinction of Koolasuchus.

8:54 AM  
Blogger starman said...

OK interesting. But what took crocodilians (or crocodylomorphs) so long to extirpate the temnospondyls, if they did? Was Australia a last refugium, like New Zealand for the Tuatara?

March 26, 2018

1:57 PM  
Blogger starman said...

Oh by the way, you can reply in the latest thread (besides reply to the alien toy post itself).

March 26, 2018

1:58 PM  
Anonymous Neal Robbins said...

By the start of the Cretaceous, there were very few temnospondyls left. They had disappeared in most places. Other factors may have been involved in addition to competition from crocodylomorphs. Australia seems to have been a last refuge for temnospondyls.

2:51 PM  

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