Question: when did equus first appear in fossil record
[{'answer': '1820s', 'provenance': [{'wikipedia_id': '10490785', 'title': 'Evolution of the horse', 'start_paragraph_id': 6, 'start_character': 95, 'end_paragraph_id': 6, 'end_character': 100, 'bleu_score': 1.0, 'section': 'Section::::History of research.\n'}]}, {'answer': 'about 3.5 mya', 'provenance': [{'wikipedia_id': '10490785', 'title': 'Evolution of the horse', 'start_paragraph_id': 51, 'start_character': 168, 'end_paragraph_id': 51, 'end_character': 181, 'bleu_score': 1.0, 'section': 'Section::::Miocene and Pliocene: true equines.:"Plesippus".\n'}]}, {'answer': '~ 3.5 million years old'}, {'provenance': [{'wikipedia_id': '10490785', 'title': 'Evolution of the horse', 'start_paragraph_id': 6, 'start_character': 0, 'end_paragraph_id': 6, 'end_character': 325, 'bleu_score': 0.965203995518735, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2730107917428778053}, 'section': 'Section::::History of research.\n'}]}, {'provenance': [{'wikipedia_id': '10490785', 'title': 'Evolution of the horse', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 0, 'bleu_score': 1.0, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2730107917428778053}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '10490785', 'title': 'Evolution of the horse', 'start_paragraph_id': 55, 'start_character': 0, 'end_paragraph_id': 55, 'end_character': 459, 'bleu_score': 0.972782728923768, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2730107917428778053}, 'section': 'Section::::Modern horses.:"Equus".\n'}]}, {'provenance': [{'wikipedia_id': '10490785', 'title': 'Evolution of the horse', 'start_paragraph_id': 51, 'start_character': 0, 'end_paragraph_id': 51, 'end_character': 447, 'bleu_score': 0.9712154609069981, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2730107917428778053}, 'section': 'Section::::Miocene and Pliocene: true equines.:"Plesippus".\n'}]}, {'provenance': [{'wikipedia_id': '10490785', 'title': 'Evolution of the horse', 'section': 'Section::::Miocene and Pliocene: true equines.:"Plesippus".\n', 'start_paragraph_id': 51, 'end_paragraph_id': 51, 'meta': {'evidence_span': ['The famous fossils found near Hagerman, Idaho were originally thought to be a part of the genus "Plesippus". Hagerman Fossil Beds (Idaho) is a Pliocene site, dating to about 3.5 mya.', 'The famous fossils found near Hagerman, Idaho were originally thought to be a part of the genus "Plesippus". Hagerman Fossil Beds (Idaho) is a Pliocene site, dating to about 3.5 mya.', 'The famous fossils found near Hagerman, Idaho were originally thought to be a part of the genus "Plesippus". Hagerman Fossil Beds (Idaho) is a Pliocene site, dating to about 3.5 mya. The fossilized remains were originally called "Plesippus shoshonensis", but further study by paleontologists determined the fossils represented the oldest remains of the genus "Equus".']}}]}, {'provenance': [{'wikipedia_id': '10490785', 'title': 'Evolution of the horse', 'section': 'Section::::Modern horses.:"Equus".\n', 'start_paragraph_id': 55, 'end_paragraph_id': 55, 'meta': {'evidence_span': ['The oldest fossil to date is ~3.5 million years old from Idaho, USA.', 'The oldest fossil to date is ~3.5 million years old from Idaho, USA. The genus appears to have spread quickly into the Old World, with the similarly aged "Equus livenzovensis" documented from western Europe and Russia. Molecular phylogenies indicate the most recent common ancestor of all modern equids (members of the genus "Equus") lived ~5.6 (3.97.8) mya.']}}]}]