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Xenosmilus hodsonae
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Xenosmilus hodsonae
 *This image is copyright of its original author Name: Xenosmilus (Foreign knife). Phonetic: Zee-no-smi-lus. Named By: Martin, Babiarz, Naples & Hearst 2000. Classification: Chordata, Mammalia, Carnivora, Felidae, Machairodontinae, Machairodontini. Species: X. hodsonae (type). Diet: Carnivore. Size: 1.7 to 1.8 meters long. Known locations: USA, Florida, Alachua County. Time period: Calabrian of the Pleistocene. Fossil representation: Remains of two almost complete individuals. Although not as famous as Smilodon, Xenosmilus was nonetheless an exceptionally powerful Pleistocene era big cat that is estimated to have weighed between 230-400 kg. This estimate puts Xenosmilus within the same weight class as the largest species of Smilodon, and even though it was smaller, Xenosmilus would have been proportionately stronger for its size.
Further readingXenosmilus had been placed within the Machairodontinae group of sabre-toothed cats, mainly because of the large forward canines. However the canines were not as long as they were in other species, although the teeth in general do seem to be more robust possibly indicating that prey was still alive and struggling when they were brought into use. However the immensely powerful build of Xenosmilus meant that it was capable of wrestling almost any prey to the ground with ease, suggesting that teeth breakage would not have to be risked. Because Xenosmilus has a powerful short legged build associated with the dirk toothed cats combined with broad upper canines as seen in the scimitar tooth cats, its exact classification has been a subject of some confusion. It could be that Xenosmilus displays a link between the two cat groups, or alternatively the features of Xenosmilus are simply a freak case of convergent evolution. Xenosmilus is estimated to have lived one million years ago during the Calabrian phase of the Pleistocene. However because only the two specimens from the same locale are known, the full temporal range of Xenosmilus in the fossil record cannot be established. However this placement does reveal that potential competition for Xenosmilus could have come from the earlier species of Smilodon, Dire wolves, and possibly the Dire wolf ancestor, Armbruster's Wolf. One of the prey animals chosen by Xenosmilus are peccaries, often referred to as New World Pigs. This is confirmed by the presence of numerous peccary bones found in association with the Xenosmilus remains, and during the Pleistocene peccaries would have provided an abundant food source. - Three ways to be a saber-toothed cat. - Naturwissenschaften 87:41-44 - L. D. Martin, J. P. Babiarz, V. L. Naples & J. Hearst - 2000. Source: http://www.prehistoric-wildlife.com/spec...milus.html 
Looks like an extremely powerful cat, nice find and info vod, I never knew about this species.
@Vodmeister :Xenosmilus, after reading the linked accounts, was a sort of like tyrannosaurid saber tooth cat... Especially when it is said "Rather than trying to trip or tackle prey and then deliver deadly slashing bites, Martin and colleagues hypothesize that Xenosmilus had a different killing method. “As the jaws closed,” Martin and co-authors wrote in their new description, “a large bolus of meat was extracted.” This cat was not a quick and elegant killer. If these paleontologists are correct, then Xenosmilus tore away large chunks of flesh from the flanks or abdomens of fleeing prey until the animal died of shock and blood loss."
Very interesting ! Thanks for sharing it... 
http://www.livescience.com/16812-saber-t...vered.html
 *This image is copyright of its original author
 Xenosmilus Part One
 *This image is copyright of its original author  *This image is copyright of its original author  *This image is copyright of its original author  *This image is copyright of its original author  *This image is copyright of its original author
I go back to what I told at #5, xenosmylus being a kind of "tyrex-saber toothed cat". From one side you have the machairodonts, smilodons and so one, being very powerful felids with a amazing weak bite force which are supposed to have brought down their prey thank to their strong front paws and only after (ie almost cautiously) delivered the deathblow by severing the artery or the jugular veins. From the other side you have the modern big cats with "normal fangs" (tigers, lions...) which get frankly in touch including shock towards the preys, the fangs being at once operationnal, efficient, the bite force is stronger but the fore limbs are not as powerful. Between them and the saber toothed cats, the xenosmylus which was able to physically control any sort of preys thanks to his very exceptionnal powerful body and his fangs being not as long as the machairodonts' ones, he could deliver at the same time the fatal bite by guting or disemboweling his prey anywhere on the body.
Perhaps the xenosmylus was not very fast because of its very stocky morphology, it must/should have laid its ambush with a very short running of attack. 
I think Xenosmilus was stronger than any other saber-tooth species pound-for-pound. It was also always my favorite saber-tooth cat since I knew of it. Shorter and stouter body than even Smilodon fatalis, better jaw structure much like modern cats, and good size (500-700 pounds), and you've got a mass killer!
(02-11-2017, 01:45 PM)Polar Wrote: I think Xenosmilus was stronger than any other saber-tooth species pound-for-pound. It was also always my favorite saber-tooth cat since I knew of it. Shorter and stouter body than even Smilodon fatalis, better jaw structure much like modern cats, and good size (500-700 pounds), and you've got a mass killer! Yes Xenosmylus was perhaps the most monstrous felid that has ever lived on Earth. But perhaps, because of that he disappeared. With him, perhaps, the "evolution option" of power/physical strength would have been too accentuated, increased. Xenosmilus Part Two
 *This image is copyright of its original author  *This image is copyright of its original author  *This image is copyright of its original author  *This image is copyright of its original author Xenosmilus Part Three - The Write-Up
All numeric references can be found in my earlier two posts.
Built of Xenosmilus hodsonae
The overall body orientation of X. hodsonae is posteriorly sloped, similar to S. populator. Its long bones were considered more robust than even S. fatalis in cases by Naples et al. (2011). However, when looking at more specimens, this does not hold true consistently. X. hodsonae is generally most robust than the lion and the tiger, comparable to S. fatalis, and overall somewhat outclassed by S. populator. On a side note, it is interesting to see how robust compared to S. fatalis the modern jaguar is.
The brachial index (radius length/ulna length * 100) of BIOPSI 101 is very low (0.80), indicating that this a closed forest animal. It is for this reason that X. hodsonae was probably more tiger or bear-like than lion-like in its the mass to bone width proportions as widening would be more for muscle foundation than running stress.
Body mass of Xenosmilus hodsonae
With four long bones, we have many different estimators. As Xenosmilus is not a giant as in the likes of the more popular Pleistocene felids, equations can be used but are far from needed. The humerus is tiger-lion sized in length, thus a mass of 200-240 kg can be applied for this measurement alone. The articular length falls in the same tiger-lion mass range. The midshaft diameter is greater proportionately than that of lion and tiger humeri if you consider the Christiansen and Harris (2005) diameters are from the midshaft as well. Based on Christansen's (1999) assertion that the least tranverse diameter of the humeral shaft is "usually located at midshaft in humerus and femur but often more proximally and distally situated in the radius and tibia, respectively," it is probably okay to. I personally feel the least traverse diameter falls a bit south the midshaft. Nonetheless, Christiansen's data is probably midshaft and thus the midshaft would provide a mass range of 240-290 kg. All in all, the humerus indicates a specimen with a mass of ~235 kg assuming built in between the lion and the tiger, and some thing closer to 270 kg assuming a more tiger-like built. The femur is short. The length based mass would on its own be around 170 kg. However, referring to the figure above about forelimb and hindlimb ratios, we see X. hodsonae had a very posteriorly sloped body mapping, thus estimating mass via femur length of a cat would be inaccurate. The femoral distal width is large for both a tiger and lion, but not exceptional. Thus a mass of 200-290 kg (yes, that's a large range but the two largest cats of today are proportioned quite differently in this regard) could apply for this measurement. The femoral midshaft diameter produces a lesser mass of 200-240 kg. Overall, if we ignore the length measurement, a mass of ~230 kg assuming built in between the lion and the tiger, and some thing closer to 270 kg assuming a more tiger-like built. Height of Xenosmilus hodsonae The shoulder height of X. hodsonae can be determined very easily thanks to the mostly complete specimen BIOPSI 101. Adding up the humerus (avg. 360.5 mm length), ulna (avg. 319 mm length), metacarpal III (only left one available, length 97.8 mm), and the scapula height (broken, I estimate it at around 60 mm vertically in standing position) and accounting for the inherent bend of the bone in natural posture, a in flesh shoulder height of 900-1000 mm is probably in okay range. The hip height would be a good 30 mm less than the shoulder height (considering the femur length (avg. 362 mm), tibia length (avg. 284.5 mm), metatarsal IV length (avg. 96.2 mm), and inominate/pelvis vertical posture height (perhaps c. 70 mm).
Very interesting, so does that mean the robusticity difference between S. fatalis and S. populator is greater than previously thought?
Perhaps in the topic 'Size Comparisons' we could have a visual of how the various saber-toothed cats stack-up against each other. Any thoughts?
(02-15-2017, 02:28 PM)Richardrli Wrote: Very interesting, so does that mean the robusticity difference between S. fatalis and S. populator is greater than previously thought? I can't say relatively to traditional thought, but Kurten and Werdelin (1990) put it well in this paragraph:  *This image is copyright of its original author The same work cites the thicker of metapodials in S. populator as reason for a more massive animal. While this probably is not the best bone to compare for robusticity, we see in data like that of Christiansen and Harris (2005) and Merriam and Stock (1932) this held true in the long bones. @ |
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