For the second post in my "What If" series, I'll be discussing whether or not Argentinosaurus actually lived in the Candeleros Formation.
Argentinosaurus from Dinosaurs: Giants of Patagonia:
Like I mentioned before in my "Were Giganotosaurus and Mapusaurus the Same Genus?" post, I was told, and read, some things about Giganotosaurus and Mapusaurus that contradicted each other over the years. After examining the two animals' skeletons, and looking up how old their formations are, I've come to three conclusions:
1. Mapusaurus (10.9-15.3 meters) is bigger than Giganotosaurus (12.4-13.1 meters). This makes sense because, back in the day, I read that Giganotosaurus didn't coexist with Argentinosaurus, and that it hunted smaller titanosaurs (despite being 13.2 meters long). Mapusaurus was the carcharodontosaurid that coexisted with Argentinosaurus, despite being 10.2 meters long. Why would a carcharodontosaurid, which evolved after a larger carcharodontosaurid, get smaller in order to hunt a larger animal? Now I know that isn't the case. We'll get back to Argentinosaurus shortly.
2. Giganotosaurus and Mapusaurus seem to have coexisted, based on microfossils discovered, and U-Pb dating done, in the Candeleros and Huincul Formations.
3. Mapusaurus roseae seems to be a species of Giganotosaurus: Giganotosaurus roseae. I mainly go with Giganotosaurus (Mapusaurus) roseae.
Now, we'll talk about Argentinosaurus again. Back when I thought that Giganotosaurus was bigger than Mapusaurus, I was perplexed when I read/was told that Giganotosaurus hunted Andesaurus, not Argentinosaurus. It confused me because Andesaurus was only 80 feet long (24.4 meters). This is small compared to the 170-foot long (51.8 meters) Argentinosaurus. I asked myself this question for years: How could the larger Giganotosaurus hunt such a smaller sauropod, while the smaller Mapusaurus hunted a bigger sauropod? Nowadays, with a larger size for Mapusaurus, along with the possibility of Mapusaurus roseae being Giganotosaurus roseae, based on my analysis, I don't fret over this question anymore. This is not the end of the story though.
A couple of years ago now, I read in Calvo (1999) about the bones of a large sauropod, called Sauropoda gen. et sp. indet., discovered in the Candeleros Formation, which is the same formation that Giganotosaurus carolinii came from. Labelled as MUCPv-251, it consisted of a possible dorsal vertebra and rib. It seems to have come from a large sauropod, and Calvo says that it might be related to Argentinosaurus (pg. 26).
Statement on the specimen from Calvo (1999) (P. 26):
Last year or so, I tried to find a way to estimate a length for this animal, but I couldn't find one. I was use to estimating dinosaur lengths based on limb and skull bones, not ribs. However, using the bones of the Chinese titanosaur Ruyangosaurus, I was able to get a size estimate for MUCPv-251.
Size Estimates for MUCPv-251:
1. Mapusaurus (10.9-15.3 meters) is bigger than Giganotosaurus (12.4-13.1 meters). This makes sense because, back in the day, I read that Giganotosaurus didn't coexist with Argentinosaurus, and that it hunted smaller titanosaurs (despite being 13.2 meters long). Mapusaurus was the carcharodontosaurid that coexisted with Argentinosaurus, despite being 10.2 meters long. Why would a carcharodontosaurid, which evolved after a larger carcharodontosaurid, get smaller in order to hunt a larger animal? Now I know that isn't the case. We'll get back to Argentinosaurus shortly.
2. Giganotosaurus and Mapusaurus seem to have coexisted, based on microfossils discovered, and U-Pb dating done, in the Candeleros and Huincul Formations.
3. Mapusaurus roseae seems to be a species of Giganotosaurus: Giganotosaurus roseae. I mainly go with Giganotosaurus (Mapusaurus) roseae.
Now, we'll talk about Argentinosaurus again. Back when I thought that Giganotosaurus was bigger than Mapusaurus, I was perplexed when I read/was told that Giganotosaurus hunted Andesaurus, not Argentinosaurus. It confused me because Andesaurus was only 80 feet long (24.4 meters). This is small compared to the 170-foot long (51.8 meters) Argentinosaurus. I asked myself this question for years: How could the larger Giganotosaurus hunt such a smaller sauropod, while the smaller Mapusaurus hunted a bigger sauropod? Nowadays, with a larger size for Mapusaurus, along with the possibility of Mapusaurus roseae being Giganotosaurus roseae, based on my analysis, I don't fret over this question anymore. This is not the end of the story though.
A couple of years ago now, I read in Calvo (1999) about the bones of a large sauropod, called Sauropoda gen. et sp. indet., discovered in the Candeleros Formation, which is the same formation that Giganotosaurus carolinii came from. Labelled as MUCPv-251, it consisted of a possible dorsal vertebra and rib. It seems to have come from a large sauropod, and Calvo says that it might be related to Argentinosaurus (pg. 26).
Statement on the specimen from Calvo (1999) (P. 26):
Info. on MUCPv-251 from Calvo (1999) (Pg. 26):
-Consists of a dorsal vertebra and rib.
-Rib is 175 cm long, but it's partial/the proximal half. ("Proximal" means closer to the body, as explained by Merriam-Webster and Lexico)
-Width at proximal end: 21 cm.
-Width at distal end: 12 cm.
-Rib is 175 cm long, but it's partial/the proximal half. ("Proximal" means closer to the body, as explained by Merriam-Webster and Lexico)
-Width at proximal end: 21 cm.
-Width at distal end: 12 cm.
-Rib is probably a dorsal, but I'm making that assumption because Calvo says that the vertebra found with the rib is probably a dorsal.
-Calvo thinks there's a possibility that these bones could be related with Argentinosaurus. However, I can't find any other papers that talk about this specimen.
-Calvo thinks there's a possibility that these bones could be related with Argentinosaurus. However, I can't find any other papers that talk about this specimen.
Last year or so, I tried to find a way to estimate a length for this animal, but I couldn't find one. I was use to estimating dinosaur lengths based on limb and skull bones, not ribs. However, using the bones of the Chinese titanosaur Ruyangosaurus, I was able to get a size estimate for MUCPv-251.
Size Estimates for MUCPv-251:
1. Proximal Part of Rib Length:
Ruyangosaurus:
Dorsal Rib Length: 127 cm (proximal portion) (Sassani and Bivens, 2017, pg. 8).
Length: 47.1 meters.
127 - 175 = 48.
48/127*100 = 37.8% increase.
47.1 m + 37.8% = 213 feet (64.9 meters).
Hypothetically Complete Rib for Ruyangosaurus:
"Huangetitan" ruyangensis' Largest Dorsal Rib Length: 293 cm (Sassani and Bivens, 2017, pg. 28).
Width: 17.2 cm (Sassani and Bivens, 2017, pg. 15).
Ruyangosaurus' Dorsal Rib Width: 18 cm (Sassani and Bivens, 2017, pg. 15).
Hypothetically Complete Rib for Ruyangosaurus:
"Huangetitan" ruyangensis' Largest Dorsal Rib Length: 293 cm (Sassani and Bivens, 2017, pg. 28).
Width: 17.2 cm (Sassani and Bivens, 2017, pg. 15).
Ruyangosaurus' Dorsal Rib Width: 18 cm (Sassani and Bivens, 2017, pg. 15).
Dorsal Rib Length (Proximal half only): 127 cm (Sassani and Bivens, 2017, pg. 8).
Body Length: 47.1 meters.
17.2 - 18 = 0.8.
0.8/17.2*100 = 4.7% increase.
293 cm + 4.7% = 306.8 cm for Ruyangosaurus' complete dorsal rib.
Hypothetically Complete Rib for MUCPv-251:
2. Hypothetically Complete Rib Length:
306.8 - 358 = 51.2.
51.2/306.8*100 = 16.7% increase.
47.1 m + 16.7% = 181 feet (55.0 meters).
Body Length: 47.1 meters.
17.2 - 18 = 0.8.
0.8/17.2*100 = 4.7% increase.
293 cm + 4.7% = 306.8 cm for Ruyangosaurus' complete dorsal rib.
Hypothetically Complete Rib for MUCPv-251:
Ruyangosaurus:
Dorsal Rib Length (Complete): 306.8 cm.
Width: 18 cm (Sassani and Bivens, 2017, pg. 15).
Width: 18 cm (Sassani and Bivens, 2017, pg. 15).
Length: 47.1 meters.
21 - 18 = 3.
3/18*100 = 16.7% increase.
306.8 + 16.7% = 358 cm for MUCPv-251's complete dorsal rib.
21 - 18 = 3.
3/18*100 = 16.7% increase.
306.8 + 16.7% = 358 cm for MUCPv-251's complete dorsal rib.
2. Hypothetically Complete Rib Length:
Ruyangosaurus:
Dorsal Rib Length (Complete): 306.8 cm.
Width: 18 cm (Sassani and Bivens, 2017, pg. 15).
Width: 18 cm (Sassani and Bivens, 2017, pg. 15).
Length: 47.1 meters.
306.8 - 358 = 51.2.
51.2/306.8*100 = 16.7% increase.
47.1 m + 16.7% = 181 feet (55.0 meters).
MUCPv-251's Total Length: 181 feet (55.0 meters).
Is MUCPv-251 Argentinosaurus?
Now that we have a size estimate for MUCPv-251, the question we have to ask now is whether or not MUCPv-251 belongs to Argentinosaurus, let alone a titanosaur? Based on the sauropod fauna discovered in the Candeleros Formation, consisting on the titanosaurs Andesaurus (80 feet long; 24.4 meters) and MMCH-Pv 47 (81 feet; 24.7 meters), and the rebbachisaur Limaysaurus (71-84 feet; 21.5-25.6 meters). Limaysaurus was bigger than the two titanosaurs, but its ribs were small.
Is MUCPv-251 Argentinosaurus?
Now that we have a size estimate for MUCPv-251, the question we have to ask now is whether or not MUCPv-251 belongs to Argentinosaurus, let alone a titanosaur? Based on the sauropod fauna discovered in the Candeleros Formation, consisting on the titanosaurs Andesaurus (80 feet long; 24.4 meters) and MMCH-Pv 47 (81 feet; 24.7 meters), and the rebbachisaur Limaysaurus (71-84 feet; 21.5-25.6 meters). Limaysaurus was bigger than the two titanosaurs, but its ribs were small.
Limaysaurus Skeleton:
I think the size of MUCPv-251 seems to put it in the titanosaur family. The width of the rib matches the widths of the titanosaurs Ruyangosaurus' and "Huangetitan" ruyangensis' rib widths. In fact, MUCPv-251's rib width was larger than both of them. Width aside, the size of this animal's bones puts it up there with Argentinosaurus! Argentinosaurus was 167 feet long (51.8 meters). Based on my estimates, MUCPv-251 was 181 feet long (55.0 meters). It was larger than Argentinosaurus!
Argentinosaurus was the largest titanosaur from South America. However, no Argentinosaurus fossils were discovered in the Candeleros Formation... As far as I know. However, MUCPv-251 seems to suggest that this might not be the case. What we do know is that its bones belong to a sauropod, as stated in Calvo (1999). Based on the size of the bones, the animal seems to have been a titanosaur. It might not be too
crazy to say that this animal was Argentinosaurus. A couple of sauropod dinosaurs from the Candeleros and Huincul Formations were found in other formations. Limaysaurus was discovered in both the Candeleros and Huincul Formations (Calvo and Salgado, 1995, pg. 15). Andesaurus was discovered in the Candeleros (Calvo, 1999, pg. 16, 22-24) (Calvo and Salgado, 1995, pg. 14), but also in the Bajo Barrea Formations. A titanosaur caudal vertebra was discovered there that has been attributed to Andesaurus (Casal et al., 2016, pg. 57). The Bajo Barrea Formation has been dated from the Albian-Turonian (Casal et al., 2009, "Abstract," "Introduction" p. 1). 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, pg. 56, "Edad de la Formacion Bajo Barreal"). Therefore, the Bajo Barrea Formation is 113-90 million years old (Albian-Turonian), and so is Andesaurus. Therefore, we cannot throw out the possibility that MUCPv-251 could be the first fossils of Argentinosaurus from the Candeleros Formation.
Based on microfossils and U-Pb dating, the Huincul Formation was also Albian-Cenomanian in age (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") (Corbella et al., 2004, "Abstract," "Characteristics and radiometric age of the tuff bed" pg. 229) (Garrido, 2010, pg. 138), just like the Candeleros Formation (Baez et al., 2000, pg. 491, "Geological Setting") (David Cannatella, 2015, "Temporal Data: Ages of Fossils and Calibration Priors," p. 20) (Tunik et al., 2010, pg. 270-271) (Di Giullo et al., 2012, pg. 600 "Results") (Garrido, 2010, pg. 134) (Halupczok et al., 2017, "Geological setting" pg. 2). The time frame of both formations makes it even more likely that MUCPv-251 could actually be Argentinosaurus.
The only other titanosaurs from the Candeleros Formation is Andesaurus and MMCH-Pv 47. Andesaurus is probably too small to be the real genus, but we only have one specimen to demonstrate this (Mannion and Calvo, 2011, "Additional Remains Referred To Andesaurus" p. 3). Perhaps Andesaurus grew larger than we've previously thought? I would like to think so, but this cannot be verified. Based on the skeleton we have now, Andesaurus is too small to be the real genus of MUCPv-251. MMCH-Pv 47 is slightly larger than Andesaurus, but we only have its vertebrae and no ribs. MMCH-Pv 47 is an unidentified titanosaur as well, so maybe comparing MUCPv-251 to it wouldn't be the best choice. Along with that, I cannot compare the specimens either way because I don't have a picture of MUCPv-251's bones. All I have are the size and width of its dorsal width. Therefore, based on the size, and width, of the bones, perhaps MMCH-Pv 47 isn't the real genus either. It's still small compared to Argentinosaurus.
Since I cannot find any other sources on MUCPv-251 other than Calvo (1999), I will place it as a titanosaur. Based on the size of the bones, this could possibly be the oldest recorded specimen of Argentinosaurus.
Update (2/4-9/21): A new large titanosaur has been discovered in the Candeleros Formation! Based on the size of the 166-cm long pubis, the animal was 170 feet long (51.7 meters), with a wider range of 119-207 feet (36.2-63.1 meters) based on the coracoid. Whether or not this mystery titanosaur is the owner of MUCPv-251 is unknown, but it's a possibility. However, this new titanosaur, catalogued as MOZ Pv 1221, proves that Giganotosaurus carolinii lived alongside massive sauropods!
As to whether or not MOZ is Argentinosaurus, the authors say that they don't know. Argentinosaurus is extremely fragmentary, so more MOZ bones will have to be excavated to see if it is a specimen of Argentinosaurus ("Discussion" para. 4):
Links:
Calvo (1999) (Pg. 26):
https://www.researchgate.net/publication/284053211_Dinosaurs_and_other_vertebrates_of_the_Lake_Ezequiel_Ramos_Mexia_Area_Neuquen-Patagonia_Argentina
Merriam-Webster. "Proximal":
https://www.merriam-webster.com/dictionary/proximal
Lexico. "Proximal":
https://www.lexico.com/en/definition/proximal
Calvo (1999) (Pg. 26):
https://www.researchgate.net/publication/284053211_Dinosaurs_and_other_vertebrates_of_the_Lake_Ezequiel_Ramos_Mexia_Area_Neuquen-Patagonia_Argentina
Merriam-Webster. "Proximal":
https://www.merriam-webster.com/dictionary/proximal
Lexico. "Proximal":
https://www.lexico.com/en/definition/proximal
Sassani and Bivens (2017) (Pg. 7-8, 15, and 28):
Link 2:
https://peerj.com/preprints/2988v1.pdf
https://psdinosaurs.blogspot.com/2018/12/size-calculations-for-herbivorous.html
Time of Candeleros and Huincul Formations:
https://psdinosaurs.blogspot.com/2020/07/were-giganotosaurus-and-mapusaurus-same_24.html
Sellers et al., (2013):
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3864407/
https://peerj.com/preprints/2988v1.pdf
Mannion and Calvo (2011) ("Additional Remains Referred To Andesaurus" p. 3):
Sizes of Other Sauropods:https://psdinosaurs.blogspot.com/2018/12/size-calculations-for-herbivorous.html
Time of Candeleros and Huincul Formations:
https://psdinosaurs.blogspot.com/2020/07/were-giganotosaurus-and-mapusaurus-same_24.html
Sellers et al., (2013):
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3864407/
