It was identified that Europasaurus was a unique dwarf species, and not a juvenile of an existing taxon like Camarasaurus, by a histology analysis of multiple specimens of Europasaurus.
The youngest specimen (DFMMh/FV 009) was shown by this analysis to lack signs of aging such as growth marks or laminar bone tissue, and is also the smallest specimen at 1.75 m (5.7 ft) in length.
Such bone tissue is an indicator of rapid growth, so the specimen is probably a young juvenile.
A larger specimen (DFMMh/FV 291.9) at 2 m (6.6 ft) shows large amounts of laminar tissue, with no growth marks present, so is likely a juvenile as well.
The next smallest specimen (DFMMh/FV 001) has shows the presence of growth marks (specifically annuli), and at the length of 3.5 m (11 ft) is possibly a subadult.
Further larger, DFMMh/FV 495 displays mature osteons as well as annuli, and is 3.7 m (12 ft).
The second largest analysed specimen (DFMMh/FV 153) also shows growth marks, but they are more frequent.
This specimen is 4.2 m (14 ft).
A single partial femur represents the largest known Europasaurus individual, at a body length of 6.2 m (20 ft).
Unlike all other specimens, this one (DFMMh/FV 415) shows the presence of lines of arrested growth, indicating it died after reaching full body size.
The internal bone is also partially lamellar, which shows it had stopped growing recently.

These combinations of growth factors show that Europasaurus developed its small size because of a largely reduced growth rate, gaining size slower than larger taxa such as Camarasaurus.
This slowing growth rate is the opposite of the general trend of sauropods and theropods, who reached greater sizes with increased growth rates.
Some of the close relatives of Europasaurus represent the largest dinosaurs known, including Brachiosaurus and Sauroposeidon.
Marpmann et al. (
2014) proposed that the small size and reduced growth rate of Europasaurus was an effect of pedomorphism, where the adults of taxa retain juvenile characteristics, such as size.
It was identified that Europasaurus was a unique dwarf species, and not a juvenile of an existing taxon like Camarasaurus, by a histology analysis of multiple specimens of Europasaurus. The youngest specimen (DFMMh/FV 009) was shown by this analysis to lack signs of aging such as growth marks or laminar bone tissue, and is also the smallest specimen at 1.75 m (5.7 ft) in length. Such bone tissue is an indicator of rapid growth, so the specimen is probably a young juvenile. A larger specimen (DFMMh/FV 291.9) at 2 m (6.6 ft) shows large amounts of laminar tissue, with no growth marks present, so is likely a juvenile as well. The next smallest specimen (DFMMh/FV 001) has shows the presence of growth marks (specifically annuli), and at the length of 3.5 m (11 ft) is possibly a subadult. Further larger, DFMMh/FV 495 displays mature osteons as well as annuli, and is 3.7 m (12 ft). The second largest analysed specimen (DFMMh/FV 153) also shows growth marks, but they are more frequent. This specimen is 4.2 m (14 ft). A single partial femur represents the largest known Europasaurus individual, at a body length of 6.2 m (20 ft). Unlike all other specimens, this one (DFMMh/FV 415) shows the presence of lines of arrested growth, indicating it died after reaching full body size. The internal bone is also partially lamellar, which shows it had stopped growing recently.
These combinations of growth factors show that Europasaurus developed its small size because of a largely reduced growth rate, gaining size slower than larger taxa such as Camarasaurus. This slowing growth rate is the opposite of the general trend of sauropods and theropods, who reached greater sizes with increased growth rates. Some of the close relatives of Europasaurus represent the largest dinosaurs known, including Brachiosaurus and Sauroposeidon. Marpmann et al. (2014) proposed that the small size and reduced growth rate of Europasaurus was an effect of pedomorphism, where the adults of taxa retain juvenile characteristics, such as size.
Europasaurus