Welcome to my "What If" series, where I'll discuss topics that are interesting to me, but might be considered controversial, or unacceptable, outside of mainstream Paleontology. First, we'll discuss Giganotosaurus and Mapusaurus, and see if they're the same genera but different species of Giganotosaurus.
"Giganotosaurus" (more likely
Mapusaurus)
from
Chased by Dinosaurs:
"Long Tooth" the
Mapusaurus from
Dinosaurs: Giants of Patagonia:
Giganotosaurus and Mapusaurus have confused me for about a decade-and-a-half now. I learned about Giganotosaurus first from Chased by Dinosaurs, and then Mapusaurus from Horizon: "Extreme Dinosaurs" and Dinosaurs: Giants of Patagonia. For a long time, I've thought that Giganotosaurus was larger than Mapusaurus, and that both of them lived at the same time. Then I read that Giganotosaurus was suppose to be older than Mapusaurus, and that Mapusaurus was larger than Giganotosaurus. However, Mapusaurus was given a length of 10.2 meters, while Giganotosaurus was given 13.2 meters. Years later, I decided to measure the bones of these two genera myself. As a result, I've discovered that Mapusaurus (10.9-15.3 meters)
was larger than Giganotosaurus (12.4-13.1 meters). However, one thing still bothered me: When did these two live? When I tried to find answers to that question, another one popped in my head: Are these two the same genus?
Well, the answers to both of these questions will be explained in this post. This has been a long journey, almost as long as my quest to find the largest T. rex specimen. I have to say that the answers that I've found blew my mind, and gave me new tips on how to study dinosaurs.
Time Period:
As I've explained before, I've read that Giganotosaurus lived before Mapusaurus. In order to figure out when these two animals lived, we need to talk about the formations where they were discovered, and what their dates are. Giganotosaurus' fossils were found in the Candeleros Formation (Coria and Salgado, 1995, pg. 225). We'll talk about the microfossils discovered in the formation first. Palynomorphs and calcareous microfossils can help prove how old a formation, or member of a formation, is (Turner and Peterson, 1999, pg. 89-90) (Marjanovic and Laurin, 2014, pg. 2) (Dinosaur National Monument, "Rhadinosteus parvus"). Avitabatrachus, a prehistoric frog (microfossil), was discovered in the Candeleros Formation. It has been dated from the Albian (Baez et al., 2000, pg. 491, "Geological Setting") to the Cenomanian (David Cannatella, 2015, "Temporal Data: Ages of Fossils and Calibration Priors," p. 20).
U-Pb, and zircon, dating from Garrido (2010) gives two dates: 97 Ma, plus or minus 3 million years, and 94 Ma (p. 134). In total, this is 100-94 Ma. Dating from Tunik et al., (2010) give a age of 104.3 Ma, plus or minus 2.5 million years, 100.5 Ma, plus or minus 2.1 million years, and 98.6 Ma, plus or minus 2.5 million years (pp. 270-271). In total, this is 106.8-98.4 Ma. Tunik et al.'s dates have been backed up by Krause et al., (2019) (p. 42). U-Pb dating from Di Giullo et al., (2012) give 102 Ma, plus or minus 2 million years, and 100 Ma, plus or minus 8 million years. Some zircon grains give a date of 105 million years (p. 560 "Results"). In total, this gives an age range of 108-92 Ma. In total, the Candeleros Formation is 108-92 Ma. This is middle Albian-early Turonian in age. Avitabatrachus helps to support this as well.
Mapusaurus was discovered in the Huincul Formation (Coria and Currie, 2006, "Abstract," pg. 74). Up to a minimum of nine individuals were found together in the formation (Bell and Coria, 2013, "Abstract"). Microflora collected in the Huincul Formation by Vallati (2001) ("Abstract") (List of Microflora), Vallati (2006) ("Abstract"), Musacchio and Vallati (2007) ("Introduction"), and Vallati (2013) ("Paleotropical representatives in Northern Patagonia" 1-1.2, "Conclusions") date to the Albian-Cenomanian. A list of microflora from Vallati (2013): Elateroplicites africaensis, Galeacornea, Fraxinoipollenites fragilis, and Cretacaeiporites scabratus, are all Albian in age (at best) (pp. 275-278) (Laboratory of Paleobotany, "Elateroplicites africaensis") (Fossilworks, "Elateroplicites africaensis") (Fossilworks,
"Galeacornea") (Fossilworks, "Fraxinoipollenites fragilis") (Laboratory of Paleobotany,
"Fraxinoipollenites fragilis") (Laboratory of Paleobotany, "Cretacaeiporites scabratus") (Fossilworks,
"Cretacaeiporites scabratus"), but Elateroplicites africaensis also extends to the Campanian
(Fossilworks, "Elateroplicites africaensis"). Galeacornea, and Cretacaeiporites scabratus, extend to the Coniacian (Fossilworks, "Galeacornea") (Fossilworks, "Cretacaeiporites scabratus"). Equisetosporites
cf. evidens comes from the Cenomanian (Fossilworks, "Equisetosporites evidens").
Corbella et al., (2004) give a radiometric age of 88 million years, plus or minus 3.9, for the formation, based on a fission-track analysis ("Abstract;" "Characteristics and radiometric age of the tuff bed," p. 229). This gives a full time frame of 91.9-84.1 Ma. The Huincul Formation is overlying (above) the Candeleros Formation (Tunik et al., 2010, p. 262 Figure 3) (Coria and Salgado, 1995, p. 226) (Coria and Currie, 2006, p. 74), which means that it is younger than the Candeleros Formation. I've given an age of 108-92 Ma for the Candeleros Formation, so I'm giving the Huincul Formation an age range of 92-84.1 Ma. This is early Turonian-late Santonian. The pollen species Elateroplicites africaensis, Galeacornea, and
Cretacaeiporites scabratus support this as well.
That's not all. Villa el Chocon, where the holotype of Giganotosaurus was discovered (Simon et al., 2017, "Abstract," pg. 3) (Tu Casu Estu Destino, "Villa el Chocon," pg. 1), is located in between the Candeleros and Huincul Formations (Simon et al., 2017, "Abstract," pg. 3). Limaysaurus was discovered in both the Candeleros and Huincul Formations (Calvo and Salgado, 1995, pg. 15), and in the Lohan Cura Formation, which is Aptian-Albian in age (Salgado et al., 2004, pg. 905). Andesaurus was discovered in the Candeleros (Calvo, 1999, pg. 16, 22-24) (Calvo and Salgado, 1995, pg. 14), but also in the Bajo Barrea Formation. A titanosaur caudal vertebra was discovered there that has been attributed to Andesaurus
(Casal et al., 2016, pg. 57 "Edad de la Formacion Bajo Barreal," pg. 57). The Bajo Barrea Formation has
been dated from the Albian-Turonian (Casal et al., 2009, "Abstract," "Introduction" p. 1, pg. 556-558). Pollen and spore samples assigned it to the Albian-Cenomanian, but radiometic dating (Ar/Ar), and U-Pb dates, place it at 99-91 million years (Casal et al., 2016, pp. 56, "Edad de la Formacion Bajo Barreal"). Therefore, the Bajo Barrea Formation is early Cenomanian-late Turonian in age, and so is Andesaurus. Also, a carcharodontosaurid tooth was found within the Bajo Barrea Formation as well (Casal et al., 2009, pp. 556-558). This could have belonged to either Giganotosaurus or Mapusaurus.
Even though Villa el Chocon is in both formations, the Candeleros is older than the Huincul Formation. However, the Huincul Formation is right on top of the Candeleros Formation. This could help support Mapusaurus as being a later, and more derived (advanced), species of Gigaotosaurus. This is called anagenesis (Merriam Webster, "Anagenesis"). In accordance with that, other coexisting dinosaurs were found in both formations, or in other formations of the same age. Other dinosaurs from formations of the same age could have coexisted with dinosaurs from the Candeleros and Huincul Formations as well. Plus, a giant new titanosaur from the Candeleros Formation, larger than any other titanosaur previously discovered from that formation, may be a specimen of Argentinosaurus. This remains to be seen though (Otero et al., 2021, "Discussion" para. 4).
Examining the Skeletons:
Now we have to tackle the second, and main, question of this post: Where Giganotosaurus and Mapusaurus the same genus? I originally thought of that back in 2016 (I think), but now the question has seeped back into my mind. According to Carrano et al., (2012), Giganotosaurus can only be distinguished by its "two pneumatic foramina on the medial side of its quadrate." Other characteristics given to Giganotosaurus from Coria and Salgado (1995) are found in other carcharodontosaurs, so they are not considered diagnostic (p. 233).
Giganotosaurus' Autapomorphy (Carrano et al., 2012, p. 233):As for Mapusaurus, I originally thought that the paper by Coria and Currie (2006) established Mapusaurus as its own distinct genus, but Carrano et al., (2012) said something that I did not expect. The authors stated that they couldn't specify any autapomorphies (defining characteristics, based on Merriam-Webster) that separate Mapusaurus from Giganotosaurus. They do say that Mapusaurus differed from Giganotosaurus in the "nasal rugosities" (bumps on nose) (pg. 235) (this was also stated in
Novas, 2009, pg. 302), and had one pneumatic foramen on the medial side of its quadrate while Giganotosaurus had two (Carrano et al., 2012, pg. 233 and 235). Mapusaurus' neural spines also seem to be larger and wider (
Novas, 2009, pg. 302).
Notes on the Autapomorphies of Mapusaurus by Carrano et al., (2012) (Pg. 235):
I decided to try and find the pneumatic foramen myself. Luckily for me, Novas et al., (2013) pointed out one pneumatic foramen on the medial side of Giganotosaurus' quadrate (pg. 13 Figure 10 "E"). However, they didn't point out the second one. I tried to look for it myself, but to no avail. I tried to look for the Mapusaurus' pneumatic foramen in Coria and Currie (2006) (pg. 83 Figure 7). Oddly enough, the pneumatic foramen, called a pneumatopore in the paper (Larson (2013) says that they're the same thing), is on the anterior side of the quadrate, not the medial side. Carrano et al., (2012) says that there's a pneumatic foramen on the medial side (p. 135), but I cannot find it in Coria and Currie (2006). Therefore, the only difference that I can spot with regards to the pneumatic foramen on the two animals' quadrates are their locations. However, both animals have only one pneumatic foramen on their quadrates. (Pneumatic foramen also fluctuate between ontogenetic, and individual, variation, according to Yun, 2015, p. 5)
Giganotosaurus' Right Quadrate (Novas et al., 2012, pg. 13 Figure 10) ("E" is the medial view) ("pf" is the pneumatic foramen):
Mapusaurus' Left Quadrate (Coria and Currie, 2006, pg. 83 Figure 7):
Update (6/22/21): Both Giganotosaurus and Mapusaurus had one pneumatic foramen on the medial sides of their quadrates.
Mapusaurus' (Left) and Giganotosaurus' (Right, C) Quadrates in Medial Views (Hendrickx et al., 2015, Figure 5 B and C). "MPF" means "medial pneumatic foramen." Scale bars are 10 cm:It looks like Giganotosaurus doesn't have anymore autapomorphies...
The biggest difference might be the two genera's skull designs. Based on my own observations, Giganotosaurus had an elongated/cone-shaped skull. Compared to Giganotosaurus, Mapusaurus had a shorter, box-shaped skull. This was also stated in Novas (2009) (p. 302). Using an analogy, Giganotosaurus skull was like a German Shepherd's, while Mapusaurus' skull was like an American Bulldog's. Despite this, both the German Shepherd and the American Bulldog are the same genus, just different species.
As of right now, we've discovered that both Giganotosaurus and Mapusaurus have at least one pneumatic foramen/pneumatopore on the medial sides of their quadrates (Carrano et al., 2012, p. 233 and 235) (Hendrickx et al., 2015, Figure 5). We will have to investigate the rugosities on the nasals next.
Mapusaurus' Nasal (Coria and Currie, 2006, Figure 3):
While we do have most of Mapusaurus' nasals preserved, there is a small problem with
Giganotosaurus': No paper seems to have the nasals shown. I had to get a picture of it from online.
Giganotosaurus' Actual Skull Remains (
Ernesto Bachmann Paleontological Museum) (
Tripadvisor):
I can't say too much about the nasals.
Mapusaurus' seems have rugosities (bumps) at the end of its nasals (near the lacrimal horn and eyes), and nothing near the nostrils.
Giganotosaurus seems to have had the same thing going on. The only problem is that I can't tell for certain.
Looking at a reconstructed skull doesn't help either. One picture of a reconstructed skull shows Mapusaurus' nasals looking similarly to how they are shown in Coria and Currie (2006).
Mapusaurus' Skull (NBC, 2006):
Another reconstructed skull shows
Mapusaurus' nasals that appear very similar to
Giganotosaurus'.
Mapusaurus Skeletons (
Nagoya City Science Museum):
Giganotosaurus Holotype Specimen MUCPv-CH 1 (Carmen Funes Municipal Museum):
As a result, I can't tell how either genera's rugosities looked.
Mapusaurus' rugosities on its nasals might be incomplete and go down to its nostrils, or not. The same goes for
Giganotosaurus. Therefore, the original form of the rugosities on both genera's nasals are uncertain at this point in time.
Links:
Image:
https://images.app.goo.gl/77MAUdVcpZr9pzvHA
Tripadvisor:
https://www.tripadvisor.es/LocationPhotoDirectLink-g2044288-i101982911-Villa_El_Chocon_Province_of_Neuquen_Patagonia.html#57186768
Welcome to Argentina:
https://www.welcomeargentina.com/elchocon/dinosaurs-museum.html
Even though the rugosities are unknown, I still wanted to research the rest of the skulls of the two animals.
1. L
acrimals:
The lacrimals of Mapusaurus seem to be flat at the top. The shaft seems to extend outwards at both sides in the beginning, and then straighten out at the bottom (Coria and Currie, 2006, Figure 5)
. This seems to coincide with Mapusaurus having a shorter ("squeezed in") skull. The lacrimal of Giganotosaurus at the top curves backwards. The shaft bends inwards, and then begins to straighten out towards the end (Coria and Salgado, 1995, pg. 225 Figure 1 "A")
. that look similar and have a large box-like opening for the postorbital.
Mapusaurus Lacrimals (Coria and Currie, 2006, Figure 4):
Giganotosaurus Lacrimal (Coria and Salgado, 1995, Figure 1 "A"):
Update (7/23/22):
According to Novas (2009), Mapusaurus' lacrimal would have been similar to Giganotosaurus' (p. 296 Figure 6.32, C):
2. Postorbitals:
Postorbitals are identical with a bump at the end of them. Both postorbitals probably overlap at the end (It's not visible in Giganotosaurus' since it's attacked to the skull). Both are also rugose (Coria and Salgado, 1995, pg. 225 Figure 1 "A") (Coria and Currie, 2006, Figure 5)
.
Mapusaurus' Postorbitals (Coria and Currie, 2006, Figure 5):
Giganotosaurus' Postorbitals
(Coria and Salgado, 1995, Figure 1 "A"):
3. Maxillas:
Both maxillas are box-like. Maxilla fenestra, and antorbital fossa, are in the same places (Coria and Salgado, 1995, pg. 225 Figure 1 "A") (Coria and Currie, 2006, Figure 2)
(Canale et al., 2014, Figure 3).
Mapusaurus Maxillas (Coria and Currie, 2006, Figure 2):
Giganotosaurus Holotype Maxilla (Canale et al., 2014, Figure 3):
(?)4. Dentaries:
Dentary has a chin that is “V-shaped,” and there is a groove on the body of the dentaries (Coria and Salgado, 1995, pg. 225 Figure "C") (Brusatte et al., 2012, Figure 2) (Coria and Currie, 2006, Figure 8). I don't know if this counts because other carcharodontosaurids, like Tyrannotitan and Carcharodontosaurus, have this chin as well. This could just be a carcharodontosaurid trait.
Giganotosaurus Neotype Specimen MUCPv-95 ("C") (Brusatte et al., 2012, Figure 2):
Mapusaurus Dentaries (Pay special attention to MCF-PVPH-108.3 in "E"-"F") (Coria and Currie, 2006, Figure 8):
5. Tooth Count:
A very important characteristic that different species of the same genera share is an equal number of teeth in their jaws. Counting teeth is necessary when comparing different genera (
Deak and McKenzie, 2016, "Conclusions") (Currie, 2003, pp. 224-225) (Carr et al., 2017, “Discussion: Ontogenetic tooth count reduction” para. 1-2) (
Holtz et al., 2004, p. 98) (Hurum and Sabath, 2003, “Conclusion” pp. 186-188), so I decided to count the number of teeth that Giganotosaurus and Mapusaurus have.
The Giganotosaurus specimen MUCPv-95 has 15 teeth in its incomplete dentary (Coria and Calvo, 1998, pg. 118 "Description," pg. 119 Figure 3), but Coria and Calvo say that, "it is possible that at least one or two more were present" (pg. 118 "Description").
Coria and Currie (2006) say that both Mapusaurus and Giganotosaurus had "12 maxilla alveoli" (holes for where the teeth would be) in their maxillas (pp. 77-78), and "15 tooth positions" in their dentaries (p. 85). It seems that Giganotosaurus and Mapusaurus had the same number of teeth in their maxillas and dentaries.
There are 8-9 denticles per 5 mm for Mapusaurus compared to 8-10 denticles per 5 mm in Giganotosaurus (Canale et al., 2014, pp. 7-8, "Description: Teeth: Denticles"). Calvo (1999) also reports a single 9-cm long Giganotosaurus tooth with "9-12 serrations present per 5 mm" (pp. 28-29). According to Young et al., (2014), denticles are serrations ("Abstract," "Introduction" p. 2). Coria and Currie (2006) reports the smallest Mapusaurus tooth has 12 denticles per 5 mm. The second smallest has 10 per 5 mm. However, it's 8-9 with larger teeth (pp. 86-87). At maximum, both Giganotosaurus and Mapusaurus had 8-12 denticles/serrations per 5 mm on their teeth.
Links:
Canale et al., (2014) (Pg. 7-8, "Description: Teeth: Denticles"):
Jorge Orlando Calvo (1999) (Pg. 28-29):
Young et al., (2014) ("Abstract," "Introduction" p. 2):
Just in case, I decided to count the teeth in two other theropods. The first was Carcharodontosaurus. Since Carcharodontosaurus is related to both Giganotosaurus and Mapusaurus, and lived during the same time but lived in Africa, I wanted to see if it had the same number of teeth.
The holotype, 1922 X 46, 51-52, had 12 teeth in its maxilla (Stromer, 1931 Part 2, pg. 6). This is the same as
Giganotosaurus and
Mapusaurus. The neotype specimen, SGN-Din 1, had 14 teeth in its maxilla (
Sereno et al., 1996, pg. 988 Figure 2 A).
Carcharodontosaurus Neotype SGN-Din 1 Skull from Sereno et al., (1996) (Pg. 988 Figure 2 "A"):
Premaxilla: 4.
Maxilla: 14.
Another specimen, MSNVE-20154, from the Museum of Natural History in Venice, has 15 teeth in its maxilla. It came from Mount Anti Atlas in Morocco, Egypt. The rocks there are said to be Aptian-Albian in age (Museum of Natural History in Venice, Teeth of Carcharodontosaurus (on maxilla cast)). I was confused as to whether or not this was actually a specimen of Eocarcharia, which came from the Aptian and has 15 teeth in its maxilla (Sereno and Brusatte, 2008, pg. 26-27). Mount Anti Atlas has rocks in it that are similar to the Kem Kem beds (Ibrahim et al., 2020, "Introduction" p. 1, Figure 1), or are the Kem Kem beds and the "Continental Intercalaire" (Cavin et al., 2010, pg. 393 “Geological Settings” p. 3). The "Continental Intercalaire' rocks appear to be Albian in age (Cavin et al., 2010, pg. 393 “Geological Settings” p. 4). It looks like this is a Carcharodontosaurus specimen.
MSNVE-20154 (Museum of Natural History in Venice):It looks like Carcharodontosaurus has four teeth in both premaxilla like Giganotosaurus and Mapusaurus, but up to 15 teeth in its maxilla. Carcharodontosaurus also had 10 denticles per 5 mm on its teeth (measured on 11/9/20 in Sereno et al., 1996, p. 988 Figure 2 C). Stromer (1931) backs this up by saying that the holotype of Carcharodontosaurus had, "18-20 serrations on a 1 cm length of margin," (p. 6 "Teeth"). Therefore, Carcharodontosaurus had 2 denticles less than Giganotosaurus and Mapusaurus. This all proves that Carcharodontosaurus was its own genus.
Links:
Museum of Natural History in Venice. Teeth of Carcharodontosaurus (on maxilla cast):
https://artsandculture.google.com/asset/teeth-of-carcharodontosaurus-on-maxilla-cast/PAH4rlYlKQd2aw?hl=en
Link 2:
https://artsandculture.google.com/art-projector/PAH4rlYlKQd2aw?hl=en
The second is Acrocanthosaurus. Acrocanthosaurus also lived during the same time as the three other carcharodontosaurids, and is a carcharodontosaurid itself, so I decided to count its teeth as well.
Skull 1 (Left Side) (Currie and Carpenter, 1999, pg. 211 Figure 3):
Premaxilla: 3.
Maxilla: 15.
Dentary: Can't tell.
Information from Eddy and Clarke (2011):
Premaxilla: 3 are present on each side (Figure 4), but notes that 4 alveoli are present ("Results: Cranial morphology of Acrocanthosaurus atokensis: Premaxilla"). Currie and Carpenter (1999) state that 4 teeth were present as well (p. 217).
Premaxilla (Figure 4):
Note: Figure 2 shows 4 premaxilla teeth, but the actual fossil shows three.
Maxilla: 15 (One is missing) (Figure 5) (Also noted in Currie and Carpenter, 1999, p. 212):Dentary: 17 (The 11th one is growing, and the 16th is missing) ("Results: Cranial morphology of Acrocanthosaurus atokensis: Dentary;" Figure 28 "A").
Dentary (Figure 28 "A"): Note: Currie and Carpenter (1999) state that there is "an unknown number of dentary tooth positions" in the dentary (p. 217), but I'll go with 17.
Update (5/15/21):
Paleofile gives 18 teeth for the dentary: Acrocanthosaurus had 4 teeth in its premaxilla, 15 in its maxilla, and up to 18 in its dentary. It also had up to 15 denticles per 5 mm (maximum) on its teeth (Coria and Currie, 2006, p. 86). This is 3 denticles greater than both Giganotosaurus and Mapusaurus, and 5 greater than Carcharodontosaurus. This proves that Acrocanthosaurus is its own genus.
Up next is Tyrannotitan. It lived in the Aptian-Albian of South America, and seems to have been the ancestor of Giganotosaurus and Mapusaurus. Up to 15 (Novas et al., 2015, p. 6) to 16 (Novas et al., 2005, p. 228) alveoli are present in Tyrannotitan's dentaries. However, when I counted the dentaries of the holotype, I got 15 alveoli, as stated in Novas et al., (2015).
Holotype (Novas et al., 2015, pg. 5 Figure 4 "C"):
Tooth Count Numbered (Made by me):Paratype Dentary (Novas et al., 2015, pg. 6 Figure 5 "B"):Alveoli visible: 13 (two are indeterminate).
It seems that Tyrannotitan had 15 teeth in its dentary, just like Giganotosaurus and Mapusaurus did. However, three of Tyrannotitan's teeth had bilobate denticles (two denticles clustered together than were separated from others) on the mesial sides (Novas et al., 2015, p. 8). This would have made Tyrannotitan have more denticles per 5 mm than both Giganotosaurus and Mapusaurus (Novas et al., 2005, p. 227 "Diagnosis" and p. 228 Figure 2 B) (Merriam Webster, "Bilobate") (Merriam Webster, "Lobes"). However, Novas et al., (2015) notes that Tyrannotitan had 2 denticles per 1 mm, as did Giganotosaurus (p. 7). This must be for the other teeth.
Links:
Novas et al., (2015) (Pg. 6):
Tyrannotitan is in a weird predicament. It has the same number of teeth in its dentary as Giganotosaurus and Mapusaurus, but different denticles compared to other carcharodontosaurs. Perhaps the fifteen teeth in their dentaries are a trait all giganotosaurini share, but the denticles help to tell them apart? Despite having bilobate serrations, Tyrannotitan did have the same amount of teeth in its dentary as in Giganotosaurus and Mapusaurus. One could place Tyrannotitan chubutensis as Giganotosaurus chubutensis...
Shaochilong:
Skull (Brusatte et al., 2010, Figure 1): Premaxilla: 4.
Maxilla: 12 (also noted in Figure 2 "C" and Table 2).
(?)Dentary: 13 (not actually preserved).
Neovenator:
Premaxilla: 5 (Also noted in Currie and Carpenter, 1999, p. 217).
Maxilla: 15.
Dentary: 15.
In total:
Giganotosaurus and Mapusaurus:
Maxilla: 12.
Dentary: 15.
Carcharodontosaurus:
Premaxilla: 4.
Maxilla: 12-15.
Acrocanthosaurus:
Premaxilla: 4.
Maxilla: 15.
Dentary: 17.
Tyrannotitan:
Dentary: 15.
Shaochilong:
Premaxilla: 4.
Maxilla: 12.
(?)Dentary: 13.
Concavenator:
Premaxilla: 4.
Maxilla: 13.
Dentary: 14.
Neovenator:
Premaxilla: 5.
Maxilla: 15.
Dentary: 15.
There are a couple of other dinosaurs that we can use as examples that are not carcharodontosaurs. One is Baryonyx and Suchomimus. A couple of papers, and a book, have proposed that Suchomimus tenerensis is actually Baryonyx tenerensis (Sues et al., 2002, p. 545) (Holtz et al., 2004, p. 98) (Paul, 2010/2016, pp. 94-95) (Henderson, 2018, "Materials and Methods" p. 2, Figure 1 and 5, Table 1-2). Looking at their teeth, both have 32 teeth on their dentaries (Sereno et al., 1998, pg. 14 Figure 1 "D") (Charig and Milner, 1997, pg. 1299 Figure 2) (Holtz et al., 2004, p. 98), 22 maxilla teeth (1 and 3 are missing for Baryonyx) (Paleofile, "Baryonyx") (Paleofile, "Suchomimus") (Sereno et al., 1998, p. 1299 Figure 2 "D"), and 7 premaxilla teeth (Charig and Milner, 1997, p. 15 Figure 2 "C") (Dal Sasso et al., 2005, p. 889) (Sereno et al., 1998, p. 14 Figure 1 "A" and "D"). Despite having taller dorsal and caudal neural spines (Sereno et al., p. 1300 Figure 3) than Baryonyx (Charig and Milner, 1997, pg. 55 Figure 44), perhaps the teeth prove that Suchomimus is actually Baryonyx tenerensis?
We also have Tyrannosaurus and Tarbosaurus. Both had the same number of denticles/serrations per mm on their premaxilla (3), maxilla (2), and dentary teeth (2) (Hurum and Sabath, 2003, pp. 186-187 "Dentition"). They also had 13 maxillary, and 15 dentary, teeth (Horner, 2011) (Larson, 2013, p. 37 Table 2.3B) (Deak and McKenzie, 2016, slides/pages 9 and 13) (Stein, 2021, p. 37, Figure 16). Some say that T. rex had less teeth than Tarbosaurus, and use this trait to separate the two genera (Hurum and Sabath, 2003, pp. 186-187 "Dentition"). Other scientists consider Tarbosaurus bataar to be Tyrannosaurus bataar (Carpenter, 1992, pp. 254-256) (Carr, 1999, pp. 499 "Phylogeny of Nemegt Tyrannosauridae") (Paul, 2010/2016, p. 115). The tooth, and serration, count might suggest that Tyrannosaurus and Tarbosaurus are indeed the same genera. This also seems to be the case with Giganotosaurus and Mapusaurus.
Links:
As for Giganotosaurus' and Mapusaurus' post-cranial skeletons:
6. The scapulacoracoids of both genera look identical and are thick (Coria and Currie, 2006, pg. 94-95) (
Novas et al., 2015, pg. 28 Figure 35).
Note: Mapusaurus' coracoid is really incomplete, as seen in Coria and Currie (2006) (pg. 95 Figure 20).
Mapusaurus Scapula (Coria and Currie, 2006, Figure 19):
Giganotosaurus (C.) carolinii's Scapula (Novas et al., 2015, Figure 35):
7. The femur heads are identical (
Cuesta et al., 2018, Figure 19) (Coria and Currie, 2006, pg. 101).
(Mapusaurus’ femur head appears to be incomplete, as shown in Coria and Curre, 2006, pg. 101).
8. The lower and fourth trochanters are identical, and in the same positions (Coria and Salgado, 1995, pg. 225-226) (Coria and Currie, 2006, pg. 101) (
Cuesta et al., 2018, Figure 19). (The lower trochanter is not observable from the side Giganotosaurus' femur was positioned in Cuesta et al., 2018, but the femur is similar to Carcharodontosaurus', as seen in Chiarenza and Cau, 2016, Figure 3. Carcharodontosaurus' femur is also similar to Mapusaurus'. Therefore, the lower trochanter should be in the same position as Carcharodontosaurus' and Mapusaurus') (Mapusaurus' fourth trochanter might be broken, as seen in Coria and Currie, 2006, pg. 101 Figure 28 "B"-"C")
9. There are grooves on both femurs (Coria and Currie, 2006, pg. 101 Figure 28 "ag") (My personal observation from
Cuesta et al., 2018, Figure 19).
10. Condyles at the bottom of both femurs that look identical (Giganotosaurus' appear to be smashed together, as seen in Cuesta et al., 2018, Figure 19). The condyles of both femurs bend in the opposite direction of the femur head (Coria and Currie, 2006, pg. 101 and 103) (
Cuesta et al., 2018, Figure 19).
Giganotosaurus Femur:
Calvo (1999) (Pg. 29):
Cuesta et al., (2018) (Figure 19 "D"):
Note: Bottom of Giganotosaurus' femur seems to be mashed together, most likely due to preservation. If reconstructed correctly, it would likely look similar to, if not exactly like, Mapusaurus' and Carcharodontosaurus'. Interestingly, Acrocanthosaurus' femur looks similar to Mapusaurus' and Carcharodontosaurus', so this seems to suggest that the bottom of Giganotosaurus' femur was slightly crushed during preservation.
Mapusaurus (C.)
roseae (Coria and Currie, 2006, Figure 28):
Note: Notice in "C" that the femur head is missing a portion between the femur head (fh) and the greater trochanter (gt). It might be that half-circle shape seen in Giganotosaurus' and Carcharodontosaurs' femurs. Also in "B"-"C," the 4th trochanter appears to have been broken off. This is evident in the picture of Giganotosaurus' femur from Calvo (1999),
Carcharodontosaurus
saharicus' Femur (Chiarenza and Cau, 2018, Figure 3):
Note: According to Stromer (1931), Carcharodontosaurus' femur looks similar, if not identical, to Mapusauru's (pg. 13-14).
11. Carrano et al., (2012) say that Mapusaurus' ilium could have been placed lower than Giganotosaurus', but the ilium appears to be incomplete so the "original shape is unknown" (pg. 235). Based on my own observation, the iliums of both genera appear to be placed in the same positions.
12. Both animals' neural spines appear to be equal in size (Personal Observation). Novas (2009) says that Giganotosaurus also had tall neural spines (pg. 301), so honestly I can't see the difference.
Giganotosaurus Skeleton (
Fernbank Museum):
Link:
https://images.app.goo.gl/jmiaG2Kjc69dfUsT9
Giganotosaurus Skeleton 2 (
Alden B. Dow Museum of Science and Art):
Links:
Picture:
https://images.app.goo.gl/SZDEEpwksQ2PgBMf8
Info. on Alden B. Dow Museum of Science and Art:
Sue White (2011):
https://www.mlive.com/entertainment/saginaw/2011/01/dinosaur_exhibit_will_thrill_k.html
Mapusaurus Skeletons (
Nagoya City Science Museum):
Note: This is the best picture that I could find of
Mapusaurus' skeleton in a good horizontal view.
Links:
Picture:
https://images.app.goo.gl/aoYzGsUo9R2aCBBM9
Nagoya City Science Museum:
http://www.ncsm.city.nagoya.jp/cgi-bin/en/exhibition_guide/exhibit.cgi?id=L210
13. Their ilia (hip bones) seem to be different. However, when I compared the two genera's ilia (using the three pictures above) to
Tyrannotitan's, it seems that its ilium was similar to
Mapusaurus' instead of
Giganotosaurus's.
Tyrannotitan's Ilium:
Mapusaurus' Ilium (Coria and Currie, 2006, pg. 99 Figure 26):
I remember Carrano et al., (2012) talking about an ilium being damaged. In Coria and Currie (2006), the
Mapusaurus ilium is relatively complete. So, maybe Carrano et al., (2012) is talking about
Giganotosaurus' ilium? Based on
Tyrannotitan's and
Mapusaurus' iliums, it seems to be the case. Even
Acrocanthosaurus' ilium, while the preacetabular blade (beginning of ilium) differs in shape a bit from the other two carcharodontosaurs, is more similar to
Tyrannotitan's and
Mapusaurus' than
Giganotosaurus'.
Acrocanthosaurus' Ilium (Currie and Carpenter, 1999, pg. 209 Figure 1):
Interestingly, Coria and Salgado (1995) originally showed
Giganotosaurus' ilium to look more like
Acrocanthosaurus' (p. 226 Figure 2):
However, modern reconstructions look different:
I'm going to go along with Carrano et al., (2012) saying that
Giganotosaurus' ilium was damaged and not
Mapusaurus', based on comparisons with
Tyrannotitan's ilium.
Giganotosaurus' coracoid was also reconstructed incorrectly (see above), so I guess its ilium went through the same thing. I would imagine that
Giganotosaurus' complete ilium would be shaped more like
Mapusaurus' instead of how modern reconstructions make it. Even
Carcharodontosaurus' ilium is identical to
Mapusaurus'.
Carcharodontosaurus Ilium (Ibrahim et al., 2020, Figure 139):
Link:
Ibrahim et al., (2020) (Figure 139):
https://zookeys.pensoft.net/article/47517/zoom/fig/1139/
Paper:
https://zookeys.pensoft.net/article/47517/
14. Both animals also lived in the same place, as explained above.
15. Another similarity, noted by
Brusatte et al., (2010), that both
Giganotosaurus and
Mapusaurus share, is
an equal ratio of the “proportion of the base of the ascending ramus of the maxilla excavated by the anteroventral corner of the antorbital fossa," which is 0.40 (Table 1).
With all of this in mind, it seems that
Giganotosaurus and
Mapusaurus could have been the same genus. Since
Giganotosaurus was named first (Coria and Salgado, 1995),
Mapusaurus roseae would be assigned as Giganotosaurus
roseae.
Giganotosaurus roseae differs from Giganotosaurus
carolinii in having a shorter, box-like skull. Giganotosaurus
carolinii had a longer, cone-shaped skull.
Conclusions:
Both Giganotosaurus and Mapusaurus seem to have a lot of similarities with each other. There are two differences between the genera that I've found: Time, and skull shape. Despite these differences, Giganotosaurus and Mapusaurus are extremely similar. Probably the most important characteristics that these two animals share is that they have the same number of teeth on each side of their maxillas (12), and dentaries (15), and they have up to 8-12 serrations per 5 mm maximum on their teeth. Tooth count, and even serration count, have been/are used to help lump, or split, different genera. Both genera also have one pneumatic foramen/pneumatopore on the medial side of their quadrates. Other physical similarities on the bodies of these two animals could be due to the two genera being phylogenetically close. However, at this point, I don't think that explanation can solve all the similarities between the two and keep them as separate genera. I think one could make the case that Mapusaurus could be considered as Giganotosaurus roseae.
Despite having some serrations/denticles that are bilobate, Tyrannotitan has 15 teeth in its dentary just like G. carolinii and G. roseae. It also has 2 serrations per 1 mm on its teeth, just like Giganotosaurus does. Perhaps one could also place Tyrannotitan chubutensis as Giganotosaurus chubutensis? I would also like to say that, until we get more information on the skeleton of Giganotosaurus (an osteology would be nice), I think one could combine the two (maybe three, including Tyrannotitan) genera into one.
Update (1/7/20): Shaochilong has a tooth count within the ratio of Giganotosaurus' (12 in maxilla). The dentary doesn't exist for Shaochilong, but the drawing depicts 13 teeth. Shaochilong also lived in the Turonian (Brusatte et al., 2010, p. 4), alongside Giganotosaurus carolinii and roseae. I think Shaochilong maortuensis could be Giganotosaurus maortuensis.
Update (3/13/21): Tyrannotitan might actually have coexisted with Giganotosaurus for about 7 million years. Krause et al., (2019) state that the Cerro Barcino Formation is 118.56-101.4 Ma (p. 35 Figure 2, and 40 Figure 6). The Candeleros Formation is 108-92 Ma (Garrido, 2010, p. 134) (Tunik et al., 2010, p. 270) (Di Giulio et al., 2012, p. 560) (Krause et al., 2019, p. 42). Tyrannotitan was discovered in the Cerro Castano Member (115.469-101.4 Ma) of the Cerro Barcino Formation (Krause et al., 2019, pp. 35 and 40, Figures 2 and 6) (Novas et al., 2005, p. 227). This, along with the dentary tooth count, could help to lump Tyrannotitan into Giganotosaurus, turning it into Giganotosaurus chubutensis.
Update (7/15/22):
Here's a list of characteristics that Giganotosaurus, Mapusaurus, and Tyrannotitan both share:
1.) All three species have a chin/ventral process or flange on their dentaries (Novas et al., 2005, p. 227) (Coria and Currie, 2006, pp. 83-84).
2.) All three species have 15 teeth in its dentary, and 2 serrations per 1 mm on its teeth (Novas et al., 2015, pp. 6-7).
3.) Both G. carolinii and G. (Mapusaurus) roseae had one pneumatopore/pneumatic foramen on the medial views of their quadrates (Hendrickx et al., 2015, Figure 5 B and C). G. (Tyrannotitan) chubutensis doesn't seem to have one preserved.
4.) All three species have tall dorsal and caudal neural spines (Novas et al., 2015, pp. 13-14, and 17) (Coria and Currie, 2006, pp. 90 and 92) (Coria and Salgado, 1995, p. 225). Coria and Salgado (1995) said that G. carolinii had tall dorsal neural archs (p. 225), but Figure 2 shows what seems to be tall dorsal neural spines as well.
5.) All three species also had similarly-shaped ilia (Novas et al., 2005, p. 227 Figure 1) (Coria and Currie, 2006, p. 99 Figure 26). G. carolinii's ilium was damaged (Carrano et al., 2012, p. 235), but it's likely that its ilium was shaped like the other two species'.
6.) All three species seem to have similarly-shaped femora, and share a large 4th trochanter (Coria and Salgado, 1995, pp. 225-226) (Coria and Currie, 2006, p. 103) (Novas et al., 2015, p. 22).
Using Microflora Dating for Formations:
Turner and Peterson (1999) ("Age," pg. 89-90):
https://books.google.com/books?hl=en&lr=&id=qeRM16ndBx4C&oi=fnd&pg=PA77&ots=W5Kj88zd2x&sig=CZ76lISv4Bbi3BXBoWcGMHGg124#v=onepage&q&f=false
Marjanovic and Laurin (2014) (Pg. 2):
https://www.researchgate.net/publication/260075695_69_Marja_Laurin_App_comp
Dinosaur National Monument ("Rhadinosteus parvus"):
https://www.nps.gov/dino/learn/nature/rhadinosteus-parvus.htm
Villa el Chocon in Candeleros and Huincul Formations:
Simon et al., (2017) ("Abstract," pg. 3):
https://www.researchgate.net/publication/318931668_A_New_Titanosaur_Sauropod_from_the_Upper_Cretaceous_of_Patagonia_NeuqueN_Province_Argentina
U-Pb, Zircon, and Other Dating:
Tunik et al., (2010) ("Abstract;" pg. 270):
https://www.academia.edu/5642253/Early_uplift_and_orogenic_deformation_in_the_Neuqu%C3%A9n_Basin_Constraints_on_the_Andean_uplift_from_U_Pb_and_Hf_isotopic_data_of_detrital_zircons
Link 2:
https://www.sciencedirect.com/science/article/abs/pii/S0040195110001642
Link 3:
https://www.researchgate.net/publication/248242916_Early_uplift_and_orogenic_deformation_in_the_Neuquen_Basin_Constraints_on_the_Andean_uplift_from_U-Pb_and_Hf_isotopic_data_of_detrital_zircons
Di Giullo et al., (2012) (Pg. 600 "Results"):
https://www.researchgate.net/publication/233851583_Detrital_zircon_provenance_from_the_Neuquen_Basin_south-central_Andes_Cretaceous_geodynamic_evolution_and_sedimentary_response_in_a_retroarc-foreland_basin
Halupczok et al., (2017) ("Geological setting" pg. 2):
https://www.researchgate.net/publication/321247624_Dinosaur_tracks_in_the_Kokorkom_Desert_Candeleros_Formation_Cenomanian_Upper_Cretaceous_Patagonia_Argentina_Implications_for_deformation_structures_in_dune_fields
Corbella et al., (2004) ("Abstract"):
https://www.researchgate.net/profile/H_Leanza/publication/263009336_First_fission-track_age_for_the_dinosaur-bearing_Neuquen_Group_Upper_Cretaceous_Neuquen_Basin_Argentina/links/0f31753987fde7ee73000000/First-fission-track-age-for-the-dinosaur-bearing-Neuquen-Group-Upper-Cretaceous-Neuquen-Basin-Argentina.pdf
Link 2:
https://www.researchgate.net/publication/263009336_First_fission-track_age_for_the_dinosaur-bearing_Neuquen_Group_Upper_Cretaceous_Neuquen_Basin_Argentina
Garrido (2010) (Pg. 134-135, and 138-139):
https://www.researchgate.net/publication/262658711_Estratigrafia_del_Grupo_Neuquen_Cretacico_Superior_de_la_Cuenca_Neuquina_Argentina_nueva_propuesta_de_ordenamiento_litoestratigrafico
Other Dinosaurs from Candeleros and Huincul Formations:
International Chronostratigraphic Chart (2020):
https://stratigraphy.org/timescale/
International Commission of Stratigraphy Website:
https://stratigraphy.org/news/130Merriam Webster. "Anagenesis":
https://groups.molbiosci.northwestern.edu/holmgren/Glossary/Definitions/Def-A/anagenesis.html
Skeletons:
Carrano et al., (2012) (Pg. 233-235):
https://www.researchgate.net/profile/Matthew_Carrano/publication/230808558_The_phylogeny_of_Tetanurae_Dinosauria_Theropoda/links/0912f504a5960e5645000000/The-phylogeny-of-Tetanurae-Dinosauria-Theropoda.pdf?origin=publication_detail
Coria and Salgado (1995) (Pg. 225 Figure 1 "A," "B," "C"):
https://vdocuments.mx/a-new-giant-carnivorous-dinosaur-from-the-cretaceous-of-patagonia.html
Coria and Currie (2006) (Figure 3, 5, 2, 7, 8, pg. 87):
https://www.researchgate.net/publication/228655543_A_new_carcharodontosaurid_Dinosauria_Theropoda_from_the_Upper_Cretaceous_of_Argentina
Canale et al., (2014) (Figure 3):
https://www.researchgate.net/figure/Maxillae-of-Mapusaurus-roseae-a-MCF-PVPH-108115-b-MCF-PVPH-108169-Acrocanthosaurus_fig3_276266912
Brusatte et al., (2012) (Figure 2):
https://bioone.org/journals/Acta-Palaeontologica-Polonica/volume-57/issue-1/app.2010.0125/A-Reassessment-of-iKelmayisaurus-petrolicus-i-a-Large-Theropod-Dinosaur/10.4202/app.2010.0125.full
2nd Link:
https://www.app.pan.pl/archive/published/app57/app20100125.pdf
3rd Link:
https://www.researchgate.net/publication/260714702_A_Reassessment_of_Kelmayisaurus_petrolicus_a_Large_Theropod_Dinosaur_from_the_Early_Cretaceous_of_China
Jorge Orlando Calvo (1999) (Pg. 28-29):
Canale et al., (2014) (Pg. 7-8, "Description: Teeth: Denticles"):
Young et al., (2014) ("Abstract," "Introduction" p. 2):
Coria and Currie (2006) (Pg. 94-95, 101, 103):
https://www.researchgate.net/publication/228655543_A_new_carcharodontosaurid_Dinosauria_Theropoda_from_the_Upper_Cretaceous_of_Argentina
Novas et al., (2015) (Pg. 38 Figure 35):
Coria and Salgado (1995) (Pg. 225-226):
https://vdocuments.mx/a-new-giant-carnivorous-dinosaur-from-the-cretaceous-of-patagonia.html
Cuesta et al., (2018) (Figure 19):
https://www.tandfonline.com/eprint/ZbyGKEjskApcGBWkrYkn/full
Chiarenza and Cau (2016) (Figure 3):
https://peerj.com/articles/1754.pdf
Stromer (1931) (Part 2) (Pg. 6, 13-14):
http://www.dinochecker.com/papers/Stromers-Egypt-expedition_Carcharodontosaurus_Stromer_1931.pdf
Brusatte et al., (2010) (Table 1):
https://pdfs.semanticscholar.org/4069/64fde0143305ce9218d4cbab4c6a54bc3a8c.pdf?_ga=2.196665772.1009657602.1594971153-1570346531.1593987467
Novas (2009) (Pg. 301):
https://books.google.com/books?id=dXYi6j7QQ-YC&pg=PA301&lpg=PA301&dq=giganotosaurus+roseae&source=bl&ots=PcWRpJnh5D&sig=ACfU3U1qfi9WhEL4f4bJE-YHw6yqAvY7BA&hl=en&sa=X&ved=2ahUKEwiBwZjntNfqAhWslHIEHQp7BxI4PBDoATAHegQICRAB#v=onepage&q=giganotosaurus%20roseae&f=falseHendrickx et al., (2015) (Figure 2 "G"):
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4579021/figure/fig-2/
Paper:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4579021/
Tyrannotitan's Ilium:
https://images.app.goo.gl/RniPPMtwNeNB7iRBA
Coria and Currie (2006) (Pg. 99 Figure 26):
https://www.researchgate.net/publication/228655543_A_new_carcharodontosaurid_Dinosauria_Theropoda_from_the_Upper_Cretaceous_of_Argentina
Carcharodontosaurus maxilla with 15 teeth:
Museum of Natural History in Venice:
https://artsandculture.google.com/asset/teeth-of-carcharodontosaurus-on-maxilla-cast/PAH4rlYlKQd2aw?hl=en
Link 2:
https://artsandculture.google.com/art-projector/PAH4rlYlKQd2aw?hl=en
Sereno and Brusatte (2008) (Pg. 26-27):
https://www.researchgate.net/publication/272152049_Basal_abelisaurid_and_carcharodontosaurid_theropods_from_the_Lower_Cretaceous_Elrhaz_Formation_of_Niger
Ibrahim et al., (2020) ("Introduction" p. 1, Figure 1):
Cavin et al., (2010) (Pg. 393 “Geological Settings” p. 3-4):
https://www.researchgate.net/publication/223833925_Vertebrate_assemblages_from_the_early_Late_Cretaceous_of_southeastern_Morocco_An_overview
Paulina-Carabajal and Canale (2010) (Figure 2):
https://www.researchgate.net/figure/Carcharodontosaurus-saharicus-SGM-Din-1-A-C-iguidensis-B-Giganotosaurus_fig2_233661959
Novas (2009):
https://books.google.com/books?id=dXYi6j7QQ-YC&pg=PA301&lpg=PA301&dq=giganotosaurus+roseae&source=bl&ots=PcWRpJnh5D&sig=ACfU3U1qfi9WhEL4f4bJE-YHw6yqAvY7BA&hl=en&sa=X&ved=2ahUKEwiBwZjntNfqAhWslHIEHQp7BxI4PBDoATAHegQICRAB#v=onepage&q=giganotosaurus%20roseae&f=false
Differences:
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