# Estimating the mass of all tetrapods on the ark

Data taken from supplementary materials included with Body Size Distribution of the Dinosaurs (PLOS One, 2012).  Masses are in kilograms.

 Class Species # Genera # Avg Species Mass Avg. Genera Mass Number on ark Total mass on ark (genera) Amphibian 6500 236 0.2 0.6 2 262 Reptile 8700 841 3.9 14.7 2 24,661 Dinosaur 1350 275 3601.4 3344.0 2 1,839,184 Bird 10000 1993 0.4 0.5 14 14,983 Mammal (no cetaceans) 5410 2023 64.8 104.4 2 422,216 Totals: 31960 5368 2,301,307

Above, average genera mass is calculated by:

1. Calculating the average mass of all species within a genera.
2. Averaging the masses of all genera within a class (bird, mammal, etc.).

By taking the average mass of species in every genera, multiplied by the number on the ark and then summing those masses, the total mass of an average species from every tetrapod genera is 2,301,307kg.  If juveniles were used it would be far less, but we'll assume 1 million kg as a conservative overestimate.

## Justification for Genera instead of Species

We calculate genera and not species because:

1. The most widely accepted definition of species [is](http://www.blackwellpublishing.com/ridley/a-z/biological_species_concept.asp) "groups of interbreeding natural populations that are reproductively isolated from other such groups." This puts geographically isolated but otherwise genetically identical organisms as diffirent species.
2. Genera can form rapidly as a genetically diverse population disperses and natural selection eliminates different alleles in each sub-population. For example, The [genus rattus](http://www.talkorigins.org/faqs/speciation.html) "currently consists of 137 species and is known to have originally developed in Indonesia and Malaysia during and prior to the Middle Ages".   Noah should not be required to take species that don't yet exist.
3. The genera or possibly the family is the closest to the concept of a created kind in genesis. In most genera and some families creationists agree all members likely shared a common ancestor. For example, homo (sapiens, erectus, denisovan neandertal, florensis), pan (chimp and bonobo), equids (horse, donkey, zebra), panthera (tiger, lion, jaguar, leopard) etc. There is not a need to take eastern gray squirrels, western gray squirrels, and red squirrels (each a separate species) on the ark.