Multiple Birth OffspringNorth AmericaPregnancy, MultipleTwinsDiseases in TwinsTwins, MonozygoticPregnancyTwins, ConjoinedTwins, DizygoticSouth AmericaAmericasLatin AmericaCentral AmericaTwin Studies as TopicPregnancy, TwinNorth CarolinaPhylogenyEuropeNorth SeaGeographyFossilsGenetic VariationPhylogeographyAsiaCanadaPaleontologyNorth DakotaAnimal MigrationDinosaursSequence Analysis, DNAEcosystemClimateRadiometric DatingPopulation DynamicsUnited StatesHistory, AncientDNA, Ribosomal SpacerBirdsMolecular Sequence DataAtlantic Ocean