Dryptosaurus aquilunguis holotype skeleton ANSP 9995 (cast) (Delaware Museum of Natural History):
Time: 72-66 million years ago, Maastrichtian of the late Cretaceous period.
Place: North America.
Length: 15-28 feet (4.6-8.4 meters).
Diet: Carnivore.
My added species:
1.
Nanotyrannus/Dryptosaurus lancensis.
Let's talk about a dinosaur that I've become intimately associated with for a couple of years now: Dryptosaurus.
Part 1: Dryptosaurus aquilunguis:
Dryptosaurus aquilunguis was a basal tyrannosauroid that lived in the Maastrichtian of the late Cretaceous period in Appalachia, North America. The holotype specimen, ANSP 9995, was recovered from the New Egypt Formation of New Jersey, which is Maastrichtian in age (Brusatte et al., 2011, pp. 1, 5, 42-43; Figure 23) (Cope, 1868, p. 100) (Brownstein, 2018, Abstract; Review: Maastrichtian: New Egypt Formation). Dryptosaurus had unique characteristics, such as interdenticle spaces (large spaces in between the large denticles/serrations) on the distal (posterior) side of the maxillary teeth, a small humerus with a large deltopectoral crest, a large manus (hand) with an elongated manual phalanx 1-1, and possibly twenty five total caudals (tail vertebrae) or more with the middle to posterior caudals being elongated (Carpenter et al., 1997, pp. 561-562 and 564; Figures 1-2) (Brusatte et al., 2011, pp. 1 and 16; Table 1; Figures 8-10) (Cope, 1868, p. 102). I've also noticed that some teeth attributed to Dryptosaurus are pinched inwards on their sides (see Brownstein, 2018, Figure 2, 5). I've obtained a body length of 28 feet (8.4 meters) for the animal.
This animal was discovered by Paleontologist Edward Drinker Cope. He originally called it "Laelaps aquilunguis" (Cope, 1868, p. 100). However, Laelaps was the name of a "mite, and this provided an opportunity for his rival, O.C. Marsh, to upstage him." Marsh renamed "Laelaps" to Dryptosaurus in 1877 (Black, 2010, para. 3-4) (Brusatte et al., 2011, p. 2).
Bones of ANSP 9995 (Cope, 1868):
Links:
ANSP 9995 (cast) Photo:
https://images.app.goo.gl/4Ma9Nwjkm8WY11Zh6
-Delaware Museum of Natural History:
https://delmns.org/metamorphosis-in-progress/Brusatte et al., (2011):
https://www.researchgate.net/publication/281043562_The_Anatomy_of_Dryptosaurus_aquilunguis_Dinosauria_Theropoda_and_a_Review_of_Its_Tyrannosauroid_AffinitiesCarpenter et al., (1997):
https://www.jstor.org/stable/4523837
Cope (1868):
https://www.biodiversitylibrary.org/page/39852079#page/109/mode/1upBrownstein (2018):
https://www.researchgate.net/publication/327117985_The_distinctive_theropod_assemblage_of_the_Ellisdale_site_of_New_Jersey_and_its_implications_for_North_American_dinosaur_ecology_and_evolution_during_the_Cretaceous
Body length:
https://psdinosaurs.blogspot.com/2022/06/size-calculations-for-dryptosaurus.html
Black (2010):
https://www.smithsonianmag.com/science-nature/how-dryptosaurus-got-its-name-68864150/Brownstein (2018):
https://palaeo-electronica.org/content/2018/2123-appalachia-biogeographyBody Size:
https://psdinosaurs.blogspot.com/2022/06/size-calculations-for-dryptosaurus.htmlPart 2: Nanotyrannus lancensis:
Nanotyrannus from Jurassic Fight Club:
Nanotyrannus is one of the most controversial dinosaurs, if not THE most controversial dinosaur, of all time! The only other dinosaur that I can think of that comes close is either Spinosaurus, or "Amphicoelias" fragillimus (now Maraapunisaurus fragillimus). I've been studying this dinosaur myself for a couple of years now, and it seems to me that this genus was closely related to Dryptosaurus. I believe that it was either Dryptosaurus aquilunguis, Dryptosaurus lancensis, or that Dryptosaurus and Nanotyrannus are sister taxa that form a clade.
Here's the history of Nanotyrannus from my post "Nanotyrannus is Dryptosaurus":
Gilmore (1946) named "Gorgosaurus lancencsis" based on the skull, CMNH 7541 (p. 2). Then, Bakker et al., (1988) changed the name to Nanotyrannus lancensis (p. 2). In between 1946 and 1988, Russell (1970) says that Gorgosaurus is actually Albertosaurus (p. 4). CMNH 7541 was then changed to "Albertosaurus lancensis" (Carpenter, 1992, pp. 258-260). Interestingly, there were two names given to this one specimen. However, Carpenter (1992) started to shake things up when he said that CMNH had features similar to T. rex, and that it was not fully grown. This led him to suggest that CMNH was a juvenile T. rex (p. 260). Now here comes the shot that was heard around the world! Carr (1999) also concluded that CMNH 7541 was a juvenile T. rex (pp. 508-509). In 2020, Carr gave an age of 8 for the specimen (Carr, 2020, Figures 2 and 12). Erickson et al., (2006) originally gave this age (Supplementary Materials, p. 13). Despite being an immature individual, some scientists still call CMNH 7541 Nanotyrannus (Currie, 2003, pp. 223-225) (Currie et al., 2003, pp. 229) (Larson, 2013, "Abstract") (Dalman et al., 2018, p. 135 Figure 15), but most scientists call Nanotyrannus a juvenile T. rex (Yun, 2015) (Woodward et al., 2020, "Abstract," "Implications for the Nanotyrannus hypothesis") (Carr, 2020, Figures 2 and 12).
CMNH 7541's Skull (Dalman et al., 2018, p. 135 Figure 15):
That was just the holotype. Now, let's talk about BMRP 2002.4.1. This specimen, also known as "Jane," was considered to be a second specimen of Nanotyrannus (Larson, 2013, "Abstract"). However, the majority of scientists put "Jane" as a juvenile T. rex (Yun, 2015) (Woodward et al., 2020, "Abstract," "Implications for the Nanotyrannus hypothesis") (Carr, 2020, Figures 2 and 12). An age of 11-13 years was given to "Jane" (Erickson et al., 2006, Supplementary Materials, p. 13) (Woodward et al., 2020, "Abstract," "Implications for the Nanotyrannus hypothesis") (Carr, 2020, Figure 2 and 12).
BMRP 2002.4.1's ("Jane's") Skeleton (Hope Babowice, 2017):
My original title for this post was "Evidence of a Subadult Nanotyrannus!?," which was based on a specimen that was discussed in a conference paper by Griffin (2014). In his paper, Griffin states that this specimen of Nanotyrannus (nicknamed “Zuri” on SWAU) shows signs of being older than a juvenile. After examining cross-sections of the specimen’s ribs, pubis, and tibia, there are signs of extensive Haversian remodeling, "longitudinal vascularization and decrease in vascularization in subperiosteal zones," and "a shift from woven to parallel-fibered bone matrix in outer growth zones." There was no sign of a external fundamental system (EFS), which signifies that the specimen has stopped growing (Stated in Stein et al., 2010, Discussion: Potential Problems: Lack of EFS), but what was present in "Zuri's" bones signified that it is not a juvenile. Griffin says that this proves that Nanotyrannus is a valid taxon (Abstract).
Griffin (2014)'s Abstract:
Nanotyrannus "Zuri's' cross-sections showing Haversian remodeling, secondary remodeled bone, and other features described above (Griffin, 2014, Figures 3-6):
"Zuri's" Rib (SWAU, HRS08467):
"Zuri's" Pubis (SWAU, HRS01514):
"Zuri's" Partial Tibia (SWAU, HRS08421):
I’ve never heard of Haversian remodeling before this, so I went on an extensive search to find out what it is. As mentioned above, Haversian remodeling does signify that the individual is either close to maturity, or is mature and even old. This is seen in apes (Lad, 2018, p. 14 Abstract), humans (Nyssen-Behets et al., 1997, Abstract), and a new titanosaur from Bulgaria (Nikolov et al., 2020). In fact, Haversian remodeling was used to help validate another pygmy dinosaur: Magyarosaurus, a dwarf titanosaur (Stein et al., 2010). It seems that Haversian remodeling might help prove that “Zuri” is a subadult Nanotyrannus. EFS was not found in “Zuri,” or Magyarosaurus, but Stein et al., (2010) said that Haversian remodeling could have gotten rid of any evidence of an EFS barrier being present (Discussion: Potential Problems: Lack of EFS). This is interesting because the Magyarosaurus specimens were around 12-14 years old (Results: Histologic Ontogenetic Stages in the M. dacus Sample, para. 1). Haversian remodeling can also remove growth rings (LAGs) from cross-sections of bones (Griffin et al., 2014, Abstract). Griffin (2014) says that “Zuri” was 12-13 when it died, but more than likely it was 13 based on the number of growth rings seen in a section of its pubis (Figure 3). This is the same age as “Jane” (Carr, 2020, Figure 12).
However, after talking to Professor Holtz, I've realized that no EFS period means that the specimen is young:
Second, I talked to Dr. Griffin himself, and to Dr. Woodward, and they both said that "Zuri" lacks extensive Haversian remodeling in its leg bones (tibia was discussed). Therefore, "Zuri" is a very young individual. Since the growth rings in its ribs give it an age of 13 at most, "Zuri" is the same age as "Jane."
Conversation with Dr. Griffin (10/11/21):
Conversation with Dr. Woodward (10/13/21):
"Zuri" is a juvenile, but there might be some evidence for two subadult Nanotyrannus specimens:
1. BMRP 2006.4.4 ("Petey"):
Woodward et al., (2020) gave this specimen an age of 15 (Results, para. 4; Discussion: Ontogenetic age, para. 1-3), based on a cross-section of its femur. Carr (2020) considers this specimen to be a subadult, and a female (Figure 12 Number 7). Professor Holtz also said that "Petey" was a subadult (Photo provided by Luke Skywalker Jedi Knight 27):
I was able to find a couple of pictures of "Petey's" manual unguals (hand claws) from Peter Larson's Twitter account. LACM 23845, a 14-16-year old specimen of T. rex (Erickson et al., 2006, Supplementary Materials, p. 13) (Carr, 2020, Figure 12 Number 8), has manual bones that are the same size as juvenile
Gorgosaurus' (Molnar, 1980, pp. 105-106), and are "quite short relative to hind limb" (Olshevsky, 1995, p. 4). The claw, although incomplete, would still seem to have been smaller than "Petey's." (Los Angeles Natural History Museum). Another young T. rex specimen, UCRC-PV1 (or UCRC PV1), has both manual unguals that are extremely short compared to "Petey's." Larson also says that UCRC is a subadult (Photo from Peter Larson's Twitter account). I also received this picture from Sebastian Dalman.
"Petey's" (white), and T. rex ("Sue" on top left, "Darwin" on top right), claw casts (Pete Larson's Twitter account):
Recently, in an abstract from Jevnikar and Zanno (2021) (SVP abstract) (p. 151), "Petey" doesn't fit inside T. rex's growth curve:
2. BHI 6437 ("Bloody Mary"):
BHI 6437, also known as the "Dueling Dinosaurs tyrannosauroid" (Raphael Rosen, 2014). No papers on this specimen have been published yet, so there's not too much to say about it. Larson said that the name of the specimen is BHI 6437 on Twitter.
BHI 6437/"Dueling Dinosaurs tyrannosauroid" Specimen (Bonhams):
BHI 6437 was stated by Carr, on his blog, to be a subadult (to my surprise) (Tyrannosauroidea central: Tyrannoethics: The naturalist T. rex and the and the T. rex list of shame, updated, 2015):
This specimen is also notorious for its giant hands:
Nanotyrannus BHI 6437 (bottom) and T. rex "Wyrex" arm bones (Alexander Jack Lund's Twitter post). Original drawing is by GetAwayTrike (Holtz, pers. comm.):
Originally, I thought that Dr. Holtz told me that the arms were incomplete (personal communication). This is a drawing he gave me earlier this year (drawing by GetAwayTrike, and edited by Denver Fowler):
However, Dalman gave me a pic. of the arm bones (pers. comm.). Holtz on Twitter did say that the arm was complete, and that he used the pic he showed me to say that "Wyrex's" arm was incomplete. I think I misunderstood him before.
Professor Holtz saying that "Bloody Mary's" arm is complete, and he explains what the above drawing originally meant (Photos provided by Luke Skywalker Jedi Knight 27):
BHI 6437's Complete Arm (Pantuso, 2019):
Longrich and Saitta (2024) said that Nanotyrannus is a basal tyrannosauroid (p. 46). Figures 33 and 34A shows Nanotyrannus alongside Dryptosaurus, Appalachiosaurus, Alioramus, and other basal tyrannosauroidea taxa (p. 47 Figure 32; p. 49 Figure 34A).
Nanotyrannus is a basal tyrannosauroid (p. 46):
Figure 33B:
Figure 34A:
On 1/4/24, Professor Holtz said that the frontal bones in the paper could "*potentially*" be from an adult
Nanotyrannus and a juvenile
Tyrannosaurus:
Special thanks to
Luke Skywalker Jedi Knight 27 for the photo of the tweet.
The juvenile
T. rex specimen is UCMP V84133 from the Hell Creek Formation (Longrich and Saitta, 2024, Figure 29):
The probable adult
Nanotyrannus specimen is DDM 334.1 (Figure 31):
Zheng et al., (2024), that placed Nanotyrannus next to Albertosaurus, Qiazhousaurus and Alioramus on their phylogenetic chart (Figure 8):
My only problem is that they put Nanotyrannus, Qiazhousaurus, and Alioramus, in the tyrannosaurinae clade. They belong in the basal tyrannosauroid clade. It's also interesting to see that they put Bistahieversor in the basal tyrannosauroid clade. I believe it's a tyrannosaurid, but that placement is intriguing nonetheless. Zheng et al., also said that "'Nanotyrannus'" is probably a juvenile T. rex, since that's the most widely-accepted hypothesis (Discussion, para. 3). It's curious that the authors still consider it to be a separate species on their phylogenetic chart though, and that its placement is similar to Longrich and Saitta (2024).
Aside from that, it's another paper saying that Nanotyrannus/Dryptosaurus lancensis is a separate genus of tyrannosaur that's distantly related to T. rex.
In his book Princeton Field Guide to Predatory Dinosaurs, Gregory S. Paul placed Nanotyrannus (and "Stygiovenator," which he put the specimens "Bloody Mary" and "Jodi" into) next to Dryptosaurus aquilunguis and Appalachiosaurus. I think he did this because both Dryptosaurus aquilunguis and Nanotyrannus/Dryptosaurus lancensis had large arms and hands. This would make Nanotyrannus/Dryptosaurus lancensis a basal tyrannosauroid (pp. 154-155). This is right before he talks about the tyrannosaurids (p. 156).
P. 154:
P. 155:
P. 156:
Rivera-Sylva and Longrich (2024) put Nanotyrannus/Dryptosaurus lancensis, and the alioramini, in the basal tyrannosauroidea clade (Figure 12):
Once again,
Bistahieversor changes clades. This time, it's in the tyrannosaurini clade. This is incorrect because the lingual bar on the medial side (interior) of its dentary covers the first alveolus only. This is consistent with basal tyrannosauroids and tyrannosaurids, not the derived tyrannosaurinae. Anyway, this is more proof of
Nanotyrannus/Dryptosaurus lancensis being a basal tyrannosauroid.
Griffin et al., (2024), an abstract from SVP 2024, studied the hyoid of CMNH 7541, along with other extinct and extant animals. The hyoid of CMNH 7541 revealed that the specimen was about 14 years old (14 LAGs "at minimum" were present in the hyoid), along with extensive (Haversian) remodeling and secondary osteons within the bone itself. The best part was that an EFS marker was found within the "outermost cortex" of the hyoid. The authors concluded that, although they're not throwing out the possibility that CMNH 7541 couldn't have been a T. rex, the best conclusion based on the evidence is that CMNH 7541 was a distinct taxon of "tyrannosaurid" that was "fully grown," (Abstract [SVP, 2024, pp. 232-233]).
Griffin et al., (2024) (
SVP, 2024):
P. 232:
P. 233:
The EFS, or External Fundamental System, indicates that an individual was mature at the time of death. Neither the 13-year old N./D. lancensis specimens BMRP 2002.4.1 ("Jane"), or the 15-year old BMRP 2006.4.4 ("Petey"), had the EFS in their limb bones (Woodward et al., 2020, p. 4). Neither does "Zuri," but "Zuri's" growth was slowing down and wasn't a juvenile despite being "at minimum 12-13 years old when it died." "Zuri" also had extensive Haversian remodeling in its bones as well (Griffin, 2014, Abstract). Both "Jane" and "Petey" were also slowing down in their growth, and they didn't fit in the Tyrannosaurus growth trajectory pattern (Jevnikar and Zanno, 2021, Abstract [SVP, 2021, p. 151]) (Longrich and Saitta, 2024, pp. 38-39). Longrich and Saitta (2024) also said that "Zuri" "was apparently near full size when it died," (p. 39). CMNH 7541, although being 14 at least, has the EFS present in its hyoid (Griffin et al., 2024, Abstract [SVP, 2024, pp. 232-233]). It seems that N./D. lancensis aged extremely quickly, and died young. Other basal tyrannosauroids that did something similar were the basal pantyrannosaurian Dilong (Xu et al., 2004, p. 680), and the eutyrannosaurian Raptorex (Sereno et al., 2009, p. 419; Supplementary Materials, p. 2). This is interesting, since I believe that Nanotyrannus/Dryptosaurus lancensis was also a basal eutyrannosaurian. Dryptosaurus aquilunguis, and Appalachiosaurus/Dryptosaurus montgomerensis, were also eutyrannosaurians (see Delcourt and Grillo, 2018).
This is amazing! I contacted Mr. Griffin back in 2021 regarding "Zuri." He was leaning towards N./D. lancensis being a juvenile T. rex at that time. I was doing so as well, even though I had my doubts. Now, his work is helping to demonstrate that the opposite is true. He actually helped to find an adult N./D. lancensis! Congratulations to him, and his team!
We finally have an adult Nanotyrannus/Dryptosaurus lancensis! Well, two of them if DDM 334.1 was an adult.
This concludes the convoluted history of
Nanotyrannus, for me anyway.
Links:
Nanotyrannus from Jurassic Fight Club pic:
https://images.app.goo.gl/JKaGXGFr7xrjkV1i9
Gilmore (1946) (PP. 2, 7, 16, and 21):
https://repository.si.edu/bitstream/handle/10088/22800/SMC_106_Gilmore_1946_13_1-19.pdf?sequence=1&isAllowed=y
Bakker et al., (1988) (PP. 2, 8-9 Table 1):
https://zenodo.org/record/1037529#.X9Ai5CVOmEf
Russell (1970) (PP. 4, 5, 7, 13-14, 15-16, and 17):
https://www.biodiversitylibrary.org/page/36032001#page/26/mode/1up
Carpenter (1992) (PP. 254-256, 258-260):
https://www.researchgate.net/profile/Kenneth_Carpenter3/publication/314988830_Tyrannosaurids_Dinosauria_of_Asia_and_North_America/links/58c8026ea6fdcca657f63102/Tyrannosaurids-Dinosauria-of-Asia-and-North-America.pdf?origin=publication_detail
Link 2:
https://www.researchgate.net/publication/314988830_Tyrannosaurids_Dinosauria_of_Asia_and_North_America
Carr (1999) (PP. 508-509, pg. 514 and 516 Table 2):
https://zenodo.org/record/3372241#.X7K6PyVOmEc
Link 2:
https://core.ac.uk/download/pdf/227005733.pdf
Carr (2020) (Figures 2 and 12):
https://peerj.com/articles/9192/
Erickson et al., (2006) (Supplementary Materials) (PP. 13-14):
http://science.sciencemag.org/content/sci/suppl/2006/07/11/313.5784.213.DC1/Erickson.SOM.pdf
Currie (2003) (Pg. 223-225):
https://www.app.pan.pl/archive/published/app48/app48-191.pdf
Currie et al., (2003) (Pg. 229):
https://www.researchgate.net/publication/40662064_Skull_structure_and_evolution_in_tyrannosaurid_dinosaurs
Larson (2013) (Abstract):
https://www.researchgate.net/publication/289687970_The_case_for_Nanotyrannus
Dalman et al., (2018) (Pg. 135 Figure 15):
https://www.researchgate.net/publication/328676947_TYRANNOSAURID_TEETH_FROM_THE_UPPER_CRETACEOUS_CAMPANIAN_TWO_MEDICINE_FORMATION_OF_MONTANA
Yun (2015) (Pg. 5):
https://www.researchgate.net/publication/308710995_Evidence_points_out_that_Nanotyrannus_is_a_juvenile_Tyrannosaurus_rex
Woodward et al., (2020) ("Abstract," "Implications for the Nanotyrannus hypothesis"):
https://advances.sciencemag.org/content/6/1/eaax6250 BHI 6437's skeleton cast:
Bonhams. "Dueling Dinosaurs":
https://www.bonhams.com/auctions/21076/lot/1032/Photo:
https://images.app.goo.gl/fgdgFdgXgcE33PwD9BHI 6437 Specimen Name:
Larson's
Twitter:
https://mobile.twitter.com/PeteLarsonTrex/status/762721220701847552
Ages of Subadult Nanotyrannus Specimens:
"Petey":
Jevnikar and Zanno (2021) (SVP, 2021, p. 151):
https://vertpaleo.org/wp-content/uploads/2021/10/SVP_2021_VirtualBook_final.pdf
Carr (2020) (Figure 12 Number 7):
https://peerj.com/articles/9192/
Woodward et al., (2020) ("Abstract," "Implications for the Nanotyrannus hypothesis"):
https://advances.sciencemag.org/content/6/1/eaax6250
BHI 6437:
Carr, Thomas. Tyrannosauroidea central. Tyrannoethics: The naturalist T. rex and the and the T. rex list of shame, updated. 2015:
https://tyrannosauroideacentral.blogspot.com/2015/02/tyrannoethics-4-naturalis-t-rex-t-rex.html
Unguals:
T. rex and Nanotyrannus Unguals from Peter Larson's Twitter post:
"Petey's" Manual Unguals:
https://mobile.twitter.com/PeteLarsonTrex/status/973337486528274432
"Petey's" Manual Ungual 2:
https://twitter.com/PeteLarsonTrex/status/770673307729457152
Drawing of BHI 6437's arm:
Fran Vidakovic's Twitter post:
https://twitter.com/Goji1999/status/1212775954667450373
BHI 6437's arm:
Pantuso (2019):
Pic:
https://images.app.goo.gl/JkCKufmnA9w5pTEH9
Article:
https://www.theguardian.com/science/2019/jul/17/montana-fossilized-dueling-dinosaurs-skeletons-dino-cowboy
Holtz's Tweet (1/4/24):
https://x.com/tomholtzpaleo/status/1742968130995945476?s=61&t=DgZNoZU2b-DFLtG5TI6cbQ
Part 3: Could Nanotyrannus be a Species of Dryptosaurus?
3.1. Did Dryptosaurus Meet Nanotyrannus?
In order to see if there's a connection between Dryptosaurus and Nanotyrannus, we need to see if the two genera could've met in real life. Dryptosaurus came from Appalachia, while Nanotyrannus came from Laramidia (Sampson et al., 2010, Figure 1). Gates et al., (2012) (Figure 1), Fiorillo and Tykosi (2014) (Results and Discussion: Laramidian Geographic Provincialism, para. 1), Bell and Currie (2014) (Figure 4), and Druckenmiller et al., (2021) (Figure 1A), all say that Laramidia and Appalachia reconnected during the late Maastrichtian, due to the Western Interior Sea receding. Blakey (2014) shows that Appalachia and Laramidia reconnected 70.8 Ma, and the Western Interior Sea basically receded considerably around 68-67 Ma (pp. 35-39).
Map of North America 66 Ma (Bell and Currie, 2014, Figure 4) ("n" means number of specimens found):
Map of North America Campanian-Maastrichtian (Druckenmiller et al., 2021, Figure 1) (Notice how Appalachia and Laramidia reconnected at the bottom):
This means that Dryptosaurus and Nanotyrannus would've been able to interact with each other. Even better though, I believe this means that Dryptosaurus could migrate from Appalachia and into Laramidia. This would've allowed Dryptosaurus to speciate, thus allowing us to speculate that Nanotyrannus could be a second species of Dryptosaurus.
3.2 Synapomorphies between Nanotyrannus and Dryptosaurus:
Now, what physical characteristics link Nanotyrannus to Dryptosaurus? This is the list that I've made so far:
1.) The labial and lingual sides of the teeth are pinched inwards in the cross-sections, unlike T. rex's.
2.) Interdenticle spaces in between the denticles, and the denticles do not meet at the top, on the distal side of the maxillary teeth. This is said to be an autopomorphy for Dryptosaurus aquiunguis (Carpenter et al., 1997, pp. 561-563), but Nanotyrannus has this too. T. rex doesn't share this characteristic.
3.) Short humeri with a large deltopectoral crest that faces anteriorly in the anterior view. T. rex's and
Daspletosaurus torosus' humeri had deltopectoral crests that veers off to the side in anterior view.
4.) A large manus with an elongated manual phalanx 1-1. Megaraptor also shares this characteristic. Juvenile T. rex specimen UCRC-PV1 doesn't share these characteristics.
5.) 25 (or so) caudals, with the middle to distal caudals being elongated.
Other basal tyrannosauroid characteristics that Nanotyrannus/Dryptosaurus lancensis has are:
1.) Small maxillary fenestra is in the middle of the antorbital fossa. Tyrannosaurus doesn't share this. The only time when the maxillary fenestra is in the middle of the antorbital fossa for Tyrannosaurus is when the premaxillary fenestra is present in the antorbital fossa. Same goes for Tarbosaurus/Tyrannosaurus bataar specimens.
2.) Premaxillary teeth that have the ridge for the serrations on the labial and lingual sides, and a vertical ridge on the distal side, of the teeth. Tyrannosaurus doesn't share this characteristic. This is seen on the T. rex hatchling specimen UCMP 119853, and the hatchling or juvenile specimen TD-13-251, which share the same morphology as the adults'. See my paper on UCMP 119853 for more info. on these two specimens.
3.) The first maxillary tooth is morphologically identical to the premaxillary teeth.
4.) The lingual bar on the medial side of the dentary covers the first alveolous/tooth. This goes for all basal tyrannosauroids and tyrannosaurids. In the derived tyrannosaurinae, the lingual bar covers the first two alveoli/teeth. This is seen in the baby T. rex specimen BHI 6439, Tarbosaurus/Tyrannosaurus bataar, and Daspletosaurus torosus and horneri. See more in my paper on BHI 6439.
5.) The first dentary tooth is conical, non-incisiform, and the serrations are on the mesial and distal sides of the tooth. Albertosaurus shares this morphology on its first dentary tooth as well. No Tyrannosaurus specimen shares this characteristic.
6.) Lacrimal horn stays present. This isn't seen in Tyrannosaurus. In hatchling Tyrannosaurus specimens, the lacrimal horn might be present. This can be seen in Tarbosaurus/Tyrannosaurus bataar hatchling specimens. However, it recedes during the juvenile stage. This is seen in the lacrimal of the juvenile T. rex specimen LACM 23845, and in older Tarbosaurus/Tyrannosaurus bataar specimens.
7.) The width of the posterior margin of the skull is smaller than publicly cited, matching that of other tyrannosaurs with thinner skull widths.
Maxillary tooth of Dryptosaurus aquilunguis holotype ANSP 9995 (Carpenter et al., 1997, p. 563 Figure 2):
Maxillary tooth of cf. Dryptosaurus specimen NJSM 12436 (Brownstein, 2018, Figure 2 number 8):
Maxillary tooth of Nanotyrannus/Dryptosaurus lancensis specimen DSTRI (Armitage, 2022, Figure 7D [DSTRI831 Mz]):
Maxillary tooth of T. rex specimen FMNH PR 2081 ("Sue") (Hendrickx et al., 2019, Figure 21 number 8):
A comparison of the distal maxillary teeth serrations/denticles of
Dryptosaurus (A and B),
Nanotyrannus (C), and
T. rex (D). Notice that the
Dryptosaurus and
Nanotyrannus serrations connect at the bottom (green arrows), but have interdenticle spaces in between them that prevent them from reconnecting at the top (light blue arrows).
T. rex's serrations have space in the middle of the serrations (light blue arrows), but they reconnect at the top (red arrows).
T. rex's serrations are hourglass-shaped. Both
Dryptosaurus and
Nanotyrannus have either rectangular-shaped, or sickle-shaped, serrations:
A is the
Dryptosaurus aquilunguis holotype specimen
ANSP 9995 from Carpenter et al., (1997) (Figure 2B). B is cf.
Dryptosaurus specimen NJSM 12436 from Brownstein (2018) (Figure 2 number 8). C is
Nanotyrannus specimen DSTRI from Armitage (2022) (Figure 7D [DSTRI831 Mz]). D is
Tyrannosaurus specimen FMNH PR 2081 from Hendrickx et al., (2019) (Figure 21 number 8).
Nanotyrannus has maxillary teeth that are pinched in on the labial and lingual sides (Bakker et al., 1988, p. 22 Figure 12):
cf. Dryptosaurus specimen NJSM 16601 has a maxillary tooth that is pinched inwards on the labial and lingual sides (green arrows added by me) (Brownstein, 2018, Figure 2 number 5):
In his 2022 preprint, Paul (2022) said that the arms of the Nanotyrannus specimen "NCMNS 'Bloody Mary'" is "longer than the femur, which is not observed in any other Campanian/Maastrichtian tyrannosaur/ids except Dryptosaurus." He also states that the arm of "Bloody Mary" is "literally as long of that as its supposed grownup T. imperator holotype, while the similar hand of another small tyrannosaurid is even longer. That does not happen in ontogeny," (p. 67). This can be seen in Figure 13 (p. 68):
Both Nanotyrannus specimens, NCMNS "Bloody Mary" and "Jodi," have hands larger than Tyrannosaurus specimen FMNH pR 2081 ("Sue"). In fact, Paul is right in saying that "Jodi's" hand is rivaling "Bloody Mary's" in size. It looks slightly larger than "Bloody Mary's!" Best of all, Paul said that the morphology of Nanotyrannus' arm is only comparable to Dryptosaurus' arm!
Compare Nanotyrannus' hand with the hand of the Dryptosaurus holotype (Brusatte et al., 2011, p. 22 Figure 12):Both taxa share an elongated manual ungual 1-1. It's longer than other tyrannosauroid manual unguals, including Gorgosaurus' (Brusatte et al., 2011, p. 47 Table 3):Jevnikar and Zanno (2021) (Abstract), and Longrich and Saitta (2024) (p. 38 Figure 25; p. 41 Figure 27), said that
Nanotyrannus/Dryptosaurus lancensis doesn't fit within the growth curve for
T. rex.
All of these traits prove to me that Nanotyrannus is related to Dryptosaurus. I prefer to name the taxon Nanotyrannus lancensis as Nanotyrannus/Dryptosaurus lancensis. I also believe that Dryptosaurus aquilunguis and Nanotyrannus/Dryptosaurus lancensis are sister taxa that make up a clade. Carpenter et al., (1997) requested to create a separate family for Dryptosaurus aquilunguis, calling it Dryptosaridae. This was originally instituted by Marsh (1890) (pp. 561 and 572). I'm using the name Dryptosauridae for a clade consisting of Dryptosaurus aquilunguis, and Nanotyrannus/Dryptosaurus lancensis.
Links:
My Nanotyrannus is Dryptosaurus post:
https://psdinosaurs.blogspot.com/2021/08/evidence-of-subadult-nanotyrannus.html
My Nanotyrannus is Dryptosaurus abstract:
https://www.academia.edu/96574784/Nanotyrannus_is_Dryptosaurus_An_Abstract
My paper on the T. rex hatchling UCMP 119853:
https://www.academia.edu/96575022/A_Baby_Tyrannosaurus_rex_Premaxillary_or_First_Maxillary_Tooth
My paper on the baby or juvenile T. rex specimen BHI 6439:
https://www.academia.edu/105502160/A_Description_of_the_Baby_T_rex_Specimen_BHI_6439
Carpenter et al., (1997):
https://www.jstor.org/stable/4523837
Brownstein (2018):
https://www.cambridge.org/core/journals/journal-of-paleontology/article/distinctive-theropod-assemblage-of-the-ellisdale-site-of-new-jersey-and-its-implications-for-north-american-dinosaur-ecology-and-evolution-during-the-cretaceous/96A7436DCD5866236C472749729F88B6
Armitage (2022):
https://www.cambridge.org/core/journals/microscopy-today/article/ultraviolet-autofluorescence-microscopy-of-nanotyrannus-lancensis-sections-reveals-blood-clots-in-vessel-canals/8222263235728A02FE7C865CFF391438
Hendrickx et al., (2019) (Dental Features in Theropods):
https://palaeo-electronica.org/content/2019/2806-dental-features-in-theropods
Bakker et al., (1988):
https://zenodo.org/record/1037529#.YmuXSyUpCEe
Paul (2022) (Preprint):
https://www.biorxiv.org/content/10.1101/2022.08.02.502517v1.full
-V2 (PDF):
https://www.biorxiv.org/content/10.1101/2022.08.02.502517v1.full.pdf
Larson (2013) (Abstract):
https://www.researchgate.net/publication/289687970_The_case_for_Nanotyrannus
Jevnikar et al., (2021) (SVP, 2021 Abstract):
https://vertpaleo.org/wp-content/uploads/2021/10/SVP_2021_VirtualBook_final.pdf
Longrich and Saitta (2024):
https://www.mdpi.com/2813-6284/2/1/1
Paul (2024):
https://books.google.com/books?id=HQIHEQAAQBAJ&printsec=frontcover&dq=Princeton+field+guide+to+dinosaurs+nanotyrannus&hl=en&newbks=1&newbks_redir=0&source=gb_mobile_search&ovdme=1&sa=X&ved=2ahUKEwj5yaL1isiHAxUKElkFHarDAaMQ6AF6BAgFEAM#v=onepage&q=Princeton%20field%20guide%20to%20dinosaurs%20nanotyrannus&f=false
Brusatte et al., (2011):
https://digitallibrary.amnh.org/bitstream/handle/2246/6117/N3717.pdf?sequence=1&isAllowed=y
Part 4: Body Length:
1.) ANSP 9995 (D. aquilunguis Holotype):
Femur (Brusatte et al., 2011, p. 27 Figure 15, A). Scale bar (first one) is 10 cm:
Length: 28 feet (8.4 meters).
2.) CMNH 7541 (Holotype of "Gorgosaurus lancensis"/Nanotyrannus lancensis):
Skull (Dalman et al., 2018, Figure 15 D):
Length: 15 feet (4.6 meters).
Age: 14 (at least), and is an adult with an EFS marker in the hyoid bone (Griffin et al., 2024 [SVP, 2024, pp. 232-233]).
3.) BMRP 2002.4.1 ("Jane"):
Skull (Brusatte et al., 2010, Figure 1, E). Scale bar is 10 cm:
Length: 22 feet (6.7 meters).
4.) BMRP 2006.4.4 ("Petey"):
Femur (Woodland et al., 2020, Supplementary Information, p. 9 Figure S2 C):
Length: 24 feet (7.4 meters).
5.) BHI 6437 ("Bloody Mary"/"Dueling Dinosaurs" specimen):
Skull (Dino Death Match, Nat Geo, 26:13):
Length: 21 feet (6.3 meters).
6.) HRS11186:
Ulna (SWAU, HRS11186). Scale bar is 10 cm:Length: 23 feet (7.1 meters).
7.) KUVP 156375 ("Laurel"):
Maxillae (Fossil Forum). I used 5 cm from the scale bar shown:Length: 23 feet (7.0 meters).
8.) HRS08 ("Zuri"):
Maxilla (SWAU, HRS08438). Scale bar is 10 cm:
Length: 21 feet (6.4 meters).
2.) CMNH 7541:
Part 5: Dryptosaurus in its Environment:
Nanotyrannus/Dryptosaurus lancensis attacking a baby Tyrannosaurus (Raul Martin, 2024; retrieved from University of Bath, 2024):
As of right now,
Dryptosaurus aquilunguis is the only large predator from the New Egypt Formation. There, it would've been the top predator (Brownstein, 2018, Results: Maastrichtian Dinosaur Faunas), until we discover a large tyrannosaurinae from the New Egypt Formation. In Laramidia, we have
Tyrannosaurus, and (?)
Dakotaraptor/a large dromaeosaur. I imagine
Nanotyrannus/Dryptosaurus lancensis being the second top predator in the Laramidian environment, underneath
Tyrannosaurus but above
(?)
Dakotaraptor/a large dromaeosaur.
Links:
University of Bath (2024):
https://www.bath.ac.uk/announcements/new-research-shows-juvenile-t-rex-fossils-are-a-distinct-species-of-small-tyrannosaur/
Brownstein (2018):
https://palaeo-electronica.org/content/2018/2123-appalachia-biogeography
My Tyrannosaurus Bio:
https://psdinosaurs.blogspot.com/2017/09/tyrannosaurus-rex-facts.html
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